Monday, November 12, 2007
Quick Fix
The Economist writes about the phenomenon of Banksy, an English graffiti artist + other viewpoints @ http://www.economist.com/daily/columns/artview/displaystory.cfm?story_id=10122228
The ART News 200: 2002
Milton Esterow writes about the world's top collectors + other viewpoints @ http://artnews.com/issues/article.asp?art_id=1164
The First Word On Pop
Barbara A. MacAdam writes about Pop art + other viewpoints @ http://www.artnews.com/anniversary/top5.asp
The Emerald Story
How does a novice differentiate between the natural and synthetic emeralds?
1. Refractive index (R.I): The refractometer is an instrument which measures the R.I of a gemstone. The R.I of a natural emerald tend to lie between 1.570 – 1.590. However, the R.I of a flux-grown synthetic emerald tend to be slightly lower, 1.563-1.566. This might be the first indication as to the authenticity of the stone, however. Care should be taken as some rare natural emeralds may also have low R.I readings. Hydrothermally grown synthetics will have R.I’s in the same range as natural stones.
2. Specific gravity (S.G): Specific gravity can be estimated using indicator liquids, or precisely using the hydrostatic method. The S.G of natural emerald is usually in the area of 2.7 – 2.8. Flux grown synthetics generally have a low S.G in the area of 2.66. Hydrothermally grown synthetics will have S.G’s in the same range as natural stones.
3. Inclusions under magnification: The nature of certain inclusions can indicate to us that an emerald is real or synthetic.
Natural emerald: Two or three phase inclusions, mineral inclusions such as calcite, pyrite, and mica, etc.
Synthetic emerald: Wispy veils of flux feathers, arrow head zoning, fine ling structural zoning, etc.
4. Chelsea Filter: A simple hand-held instrument, designed originally differentiate between emeralds and other green simulants. When viewed through this filter, a natural emerald appears anywhere from green to light pink, to red, depending on the chromium content in the stone. The more the chromium present, the more red it appears under the filter. On the other hand, many synthetic emeralds appear a striking or (hot coal) red under filter. Today many synthetic emeralds have been deliberately produced with a lower chromium content so this test should be used only with caution.
5. Others: More sophisticated means of identification are available to the lab gemologist, such as infra-red spectroscopy, and energy dispersive x-ray fluorescence. Therefore, if doubt exists, the stone should be submitted to a reputable gem testing laboratory for examination.
Imitations of emerald (natural or man-made)
An imitation of a gemstone is a material (natural or otherwise) that has same general appearance as the gem it imitates, but does not have the same chemical and/or physical properties, i.e. an imitation stone only looks like the gemstone it imitates. Some of the materials that might be mistaken for emerald are the natural gems: green tourmaline and peridot, the altered gems: dyed agate, dyed green quartz, and green glass.
Identification: The properties of these imitations differ markedly from those of natural emerald, e.g. R.Is, S.G’s, and inclusions. It should therefore be relatively easy to differentiate between these and natural emeralds.
Examples of possible imitations of emeralds and their properties
Green tourmaline
R.I = 1.62-1.64
S.G = 3.05
Inclusions = Flat liquid-filled feathers, growth tubes, etc.
Peridot
R.I = 1.65 – 1.69
S.G = 3.34
Inclusions = Lily-pad-like inclusions, etc.
Jadeite (green)
R.I = 1.66
S.G = 3.33
Inclusions = Granular appearance, etc.
Dyed Green Quartz
R.I = 1.544 – 1.553
S.G = 2.65
Inclusions = Concentration of dye in cracks, etc.
Green Glass
R.I = 1.44 – 1.69
S.G = 2 – 4.2
Inclusions = Gas bubbles, swirl structures.
Composite stones
More common imitations of emerald are composite stones or as they are often referred to doublets/triplets. Doublets have the appearance of one whole stone but are an assembly of two pieces of stone using a colored adhesive. Generally, the junctions of the two pieces may be seen in the area of the girdle (however, with garnet-topped doublets this may not be the case). The most common emerald doublets are formed using two pieces of colorless beryl to form the top and bottom, and these are cemented together with a green colored layer in the area of the girdle.
Identification: Composite stones are easily detected upon immersion in a liquid. The green junction is easily visible dividing the top and bottom when the stone is viewed, with a lens or microscope, in profile.
The grading of emerald
As with any other gemstone, the four C’s determine the value of emerald. These are color, clarity, cut and carat weight.
Color: This is the most important determinant of value. An included stone with good color will fetch a higher price than a clean stone with a weak color. Deep, pure green is desirable. Any variation of the green shade can fetch a good price provided there is depth of color.
Clarity: Emeralds are characterized by the fact that they almost invariably contain inclusions. It is very hard to find a flawless emerald with the desired color. The location of the inclusion plays a vital role in the valuation. If a flaw is very prominent on the crown of the stone, it could bring down the price. But if the same flaw were present in a more subtle position, the ultimate value would not be affected.
Cut: The depth of color and apparent clarity of a gemstone is to a certain extent the function of its cut. A well cut stone could improve the depth of color and mask certain flaws, thereby upgrading the stone. The emerald cut is ideal for emeralds for a given quality. Depending upon the number of inclusions and color, other cuts are employed, e.g. cabochons, beads, rounds, hearts, fancy cuts, etc.
Carat weight: The value of a gemstone is calculated by multiplying price/carat into total carat weight. Hence, the more the weight, the higher the potential return. Size also affects the price per carat. This is because it is very rare these days to find a large-sized emerald of an acceptable quality. Given two stones of the same quality, the one significantly larger will fetch a higher market price per carat. If two stones are of the same size and quality and thus form a pair the price per carat of the pair jumps up.
How the market operates
There is no centrally operated and controlled market for emeralds, as one has for diamonds. The mining process is largely carried out by private companies in most countries, and a few mines are run by governments. The rough stones procured are cleaned and sorted into parcels by the mine owners. The main mines are in Colombia and Brazil. Buyers come from all over the world to bid for and buy these rough parcels. These are then taken to the cutting and wholesale centers in New York, India, Israel, Germany, Hong Kong among others. Wholesale and retail buyers from all over the world come to these centers to buy faceted emeralds. These are subsequently set in jewelry and sold to the ultimate consumers.
1. Refractive index (R.I): The refractometer is an instrument which measures the R.I of a gemstone. The R.I of a natural emerald tend to lie between 1.570 – 1.590. However, the R.I of a flux-grown synthetic emerald tend to be slightly lower, 1.563-1.566. This might be the first indication as to the authenticity of the stone, however. Care should be taken as some rare natural emeralds may also have low R.I readings. Hydrothermally grown synthetics will have R.I’s in the same range as natural stones.
2. Specific gravity (S.G): Specific gravity can be estimated using indicator liquids, or precisely using the hydrostatic method. The S.G of natural emerald is usually in the area of 2.7 – 2.8. Flux grown synthetics generally have a low S.G in the area of 2.66. Hydrothermally grown synthetics will have S.G’s in the same range as natural stones.
3. Inclusions under magnification: The nature of certain inclusions can indicate to us that an emerald is real or synthetic.
Natural emerald: Two or three phase inclusions, mineral inclusions such as calcite, pyrite, and mica, etc.
Synthetic emerald: Wispy veils of flux feathers, arrow head zoning, fine ling structural zoning, etc.
4. Chelsea Filter: A simple hand-held instrument, designed originally differentiate between emeralds and other green simulants. When viewed through this filter, a natural emerald appears anywhere from green to light pink, to red, depending on the chromium content in the stone. The more the chromium present, the more red it appears under the filter. On the other hand, many synthetic emeralds appear a striking or (hot coal) red under filter. Today many synthetic emeralds have been deliberately produced with a lower chromium content so this test should be used only with caution.
5. Others: More sophisticated means of identification are available to the lab gemologist, such as infra-red spectroscopy, and energy dispersive x-ray fluorescence. Therefore, if doubt exists, the stone should be submitted to a reputable gem testing laboratory for examination.
Imitations of emerald (natural or man-made)
An imitation of a gemstone is a material (natural or otherwise) that has same general appearance as the gem it imitates, but does not have the same chemical and/or physical properties, i.e. an imitation stone only looks like the gemstone it imitates. Some of the materials that might be mistaken for emerald are the natural gems: green tourmaline and peridot, the altered gems: dyed agate, dyed green quartz, and green glass.
Identification: The properties of these imitations differ markedly from those of natural emerald, e.g. R.Is, S.G’s, and inclusions. It should therefore be relatively easy to differentiate between these and natural emeralds.
Examples of possible imitations of emeralds and their properties
Green tourmaline
R.I = 1.62-1.64
S.G = 3.05
Inclusions = Flat liquid-filled feathers, growth tubes, etc.
Peridot
R.I = 1.65 – 1.69
S.G = 3.34
Inclusions = Lily-pad-like inclusions, etc.
Jadeite (green)
R.I = 1.66
S.G = 3.33
Inclusions = Granular appearance, etc.
Dyed Green Quartz
R.I = 1.544 – 1.553
S.G = 2.65
Inclusions = Concentration of dye in cracks, etc.
Green Glass
R.I = 1.44 – 1.69
S.G = 2 – 4.2
Inclusions = Gas bubbles, swirl structures.
Composite stones
More common imitations of emerald are composite stones or as they are often referred to doublets/triplets. Doublets have the appearance of one whole stone but are an assembly of two pieces of stone using a colored adhesive. Generally, the junctions of the two pieces may be seen in the area of the girdle (however, with garnet-topped doublets this may not be the case). The most common emerald doublets are formed using two pieces of colorless beryl to form the top and bottom, and these are cemented together with a green colored layer in the area of the girdle.
Identification: Composite stones are easily detected upon immersion in a liquid. The green junction is easily visible dividing the top and bottom when the stone is viewed, with a lens or microscope, in profile.
The grading of emerald
As with any other gemstone, the four C’s determine the value of emerald. These are color, clarity, cut and carat weight.
Color: This is the most important determinant of value. An included stone with good color will fetch a higher price than a clean stone with a weak color. Deep, pure green is desirable. Any variation of the green shade can fetch a good price provided there is depth of color.
Clarity: Emeralds are characterized by the fact that they almost invariably contain inclusions. It is very hard to find a flawless emerald with the desired color. The location of the inclusion plays a vital role in the valuation. If a flaw is very prominent on the crown of the stone, it could bring down the price. But if the same flaw were present in a more subtle position, the ultimate value would not be affected.
Cut: The depth of color and apparent clarity of a gemstone is to a certain extent the function of its cut. A well cut stone could improve the depth of color and mask certain flaws, thereby upgrading the stone. The emerald cut is ideal for emeralds for a given quality. Depending upon the number of inclusions and color, other cuts are employed, e.g. cabochons, beads, rounds, hearts, fancy cuts, etc.
Carat weight: The value of a gemstone is calculated by multiplying price/carat into total carat weight. Hence, the more the weight, the higher the potential return. Size also affects the price per carat. This is because it is very rare these days to find a large-sized emerald of an acceptable quality. Given two stones of the same quality, the one significantly larger will fetch a higher market price per carat. If two stones are of the same size and quality and thus form a pair the price per carat of the pair jumps up.
How the market operates
There is no centrally operated and controlled market for emeralds, as one has for diamonds. The mining process is largely carried out by private companies in most countries, and a few mines are run by governments. The rough stones procured are cleaned and sorted into parcels by the mine owners. The main mines are in Colombia and Brazil. Buyers come from all over the world to bid for and buy these rough parcels. These are then taken to the cutting and wholesale centers in New York, India, Israel, Germany, Hong Kong among others. Wholesale and retail buyers from all over the world come to these centers to buy faceted emeralds. These are subsequently set in jewelry and sold to the ultimate consumers.
Ice Road Truckers
Here is an interesting website on Ice Road Truckers @ Ice Road Truckers + History Channel: link. Ice road trucking is considered one of the dangerous jobs + the vital supplies they carry to diamond mines over frozen lakes that double as roads is an unparalleled adventure.
Useful link:
http://www.history.com/minisites/iceroadtruckers
Useful link:
http://www.history.com/minisites/iceroadtruckers
Jean-Baptiste Tavernier’s Travels In India
Concerning Diamonds, And The Mines And Rivers Where They Are Found; And Especially Of The Author’s Journey To The Mine Of Rammalakota
(via Jean-Baptiste Tavernier’s Travels In India / V Ball / Edited by William Crooke)
I have known them to weight a stone with 150 livres of lead. It is true that it was a large stone, which weighed 130 carats after it had been cut, and that the mill was like ours, the large wheel of which was turned by four blacks. The Indians do not agree with us in believing that weighting them causes flaws in the stones. If theirs do not receive any it is because they always have a small boy who holds in his hand a very thin wooden spoon, with which he anoints the wheel incessantly with oil and diamond powder. Besides this their wheel does not go fast as ours, because the wooden wheel which causes the steel one to revolve is seldom more than 3 feet in diameter.
The Indians are unable to give the stones such a lively polish as we give in Europe; this, I believe, is due to the fact that their wheels do not run so smoothly as ours. For, being made of steel, in order to grind it on the emery, of which it has need every twenty-four hours, it has to be taken off the tree, and it cannot be replaced so as to run as evenly as it should do. If they possessed the iron wheel like ours, for which not emery but the file is required, it it not necessary to remove it from the tree in order to file it, and they could give the stones a better polish than they do. I have stated that it is necessary to rub the wheel with emery or to file it every twenty-four hours, and it is desirable that this should be done every twelve hours if the workman is not lazy. For when the stone has run a certain time, the part of the wheel where it has pressed becomes polished like a mirror, and if the place be not roughened by emery or the file, the powder does not stick to it. When it does adhere more work can be done in one hour than in two when there is none on the wheel.
Although a particular diamond may be by nature hard, having, so to speak, a kind of knot, such as is seen in wood, the Indian diamond-cutters would not hesitate to cut such a stone, although our diamond cutters in Europe would experience great difficulty in doing so, and as a general rule would be unwilling to undertake it; but the Indians are paid something extra for their trouble.
I come to the government at the mines. Business is conducted with freedom and fidelity. Two percent, on all purchases is paid to the King, who receives also a royalty from the merchants for permission to mine. These merchants having prospected with the aid of the miners, who know the spots where the diamonds are to be found, take an area of about 200 paces in circumference, where they employ fifty miners, and sometimes a hundred if they wish the work to proceed rapidly. From the day they commence mining till they finish the merchants pay a duty of 2 pagodas per diem for fifty men, and 4 pagodas when they employ a hundred men.
These poor people only earn 3 pagodas per annum, although they must be men who thoroughly understand their work. As their wages are so small they do not show any scruple, when searching the sand, in concealing a stone for themselves when they can, and being naked, save for a small cloth which covers their private parts, they adroitly contrive to swallow it. The chief of all the merchants who embark in mining one day pointed out to me one of these miners, who had worked for him for many years, and who had stolen a stone from him which weighed a mangelin, i.e. nearly two of our carats. He had concealed it in the corner of his eye, but it was taken from him as soon as the theft was discovered. In order to prevent these knavish tricks there are always twelve to fifteen watchmen employed by the merchants to see that they are not defrauded. If by chance a stone is found which weighs above 7 to 8 mangelins, it is taken to the master of the mine, who by way of recompense gives a sarpo, which is a piece of cotton cloth to make a turban, of the value of 25 to 30 sols, and generally with it half a pagoda in silver, or else a pagoda, when rice and a plate of sugar are not given.
The merchants who visit the mine to buy, remain in their dwellings, and every morning at from 10 to 11 o’clock the masters of the miners, after they have dined (for the Banians never leave their houses till they have washed and eaten), take their diamonds to show to them. If the parcels are large, and contain many stones of the value of from 2000 up to 15000 or 16000 ecus, they entrust them to the foreign merchant for seven or eight days or more in order that he may examine them with care. When the stones have been examined, and are returned by the merchant, if they suit him he should conclude the transactions at once, otherwise the owner of the stones wraps them in a corner of his waistband, his turban, or his shirt, and departs, so that one never sees the same stones again, or at least they are mixed with others, when the miner returns with another parcel. When the transaction is concluded the purchaser gives an order for payment on the Shroff or person who issues and receives bills of exchange. If you have agreed to pay in three or four days, and delay longer, you have to pay interest at the rate of 1½ percent per month. Most frequently, when the merchant is known to be solvent, a bill of exchange on Agra, Golkonda, or Bijapur is preferred, but more especially one upon Surat, where, as it is the most famous port in India, the dealers desire to purchase the commodities which come in vessels from foreign countries, and are suitable for their wants.
Jean-Baptiste Tavernier’s Travels In India (continued)
(via Jean-Baptiste Tavernier’s Travels In India / V Ball / Edited by William Crooke)
I have known them to weight a stone with 150 livres of lead. It is true that it was a large stone, which weighed 130 carats after it had been cut, and that the mill was like ours, the large wheel of which was turned by four blacks. The Indians do not agree with us in believing that weighting them causes flaws in the stones. If theirs do not receive any it is because they always have a small boy who holds in his hand a very thin wooden spoon, with which he anoints the wheel incessantly with oil and diamond powder. Besides this their wheel does not go fast as ours, because the wooden wheel which causes the steel one to revolve is seldom more than 3 feet in diameter.
The Indians are unable to give the stones such a lively polish as we give in Europe; this, I believe, is due to the fact that their wheels do not run so smoothly as ours. For, being made of steel, in order to grind it on the emery, of which it has need every twenty-four hours, it has to be taken off the tree, and it cannot be replaced so as to run as evenly as it should do. If they possessed the iron wheel like ours, for which not emery but the file is required, it it not necessary to remove it from the tree in order to file it, and they could give the stones a better polish than they do. I have stated that it is necessary to rub the wheel with emery or to file it every twenty-four hours, and it is desirable that this should be done every twelve hours if the workman is not lazy. For when the stone has run a certain time, the part of the wheel where it has pressed becomes polished like a mirror, and if the place be not roughened by emery or the file, the powder does not stick to it. When it does adhere more work can be done in one hour than in two when there is none on the wheel.
Although a particular diamond may be by nature hard, having, so to speak, a kind of knot, such as is seen in wood, the Indian diamond-cutters would not hesitate to cut such a stone, although our diamond cutters in Europe would experience great difficulty in doing so, and as a general rule would be unwilling to undertake it; but the Indians are paid something extra for their trouble.
I come to the government at the mines. Business is conducted with freedom and fidelity. Two percent, on all purchases is paid to the King, who receives also a royalty from the merchants for permission to mine. These merchants having prospected with the aid of the miners, who know the spots where the diamonds are to be found, take an area of about 200 paces in circumference, where they employ fifty miners, and sometimes a hundred if they wish the work to proceed rapidly. From the day they commence mining till they finish the merchants pay a duty of 2 pagodas per diem for fifty men, and 4 pagodas when they employ a hundred men.
These poor people only earn 3 pagodas per annum, although they must be men who thoroughly understand their work. As their wages are so small they do not show any scruple, when searching the sand, in concealing a stone for themselves when they can, and being naked, save for a small cloth which covers their private parts, they adroitly contrive to swallow it. The chief of all the merchants who embark in mining one day pointed out to me one of these miners, who had worked for him for many years, and who had stolen a stone from him which weighed a mangelin, i.e. nearly two of our carats. He had concealed it in the corner of his eye, but it was taken from him as soon as the theft was discovered. In order to prevent these knavish tricks there are always twelve to fifteen watchmen employed by the merchants to see that they are not defrauded. If by chance a stone is found which weighs above 7 to 8 mangelins, it is taken to the master of the mine, who by way of recompense gives a sarpo, which is a piece of cotton cloth to make a turban, of the value of 25 to 30 sols, and generally with it half a pagoda in silver, or else a pagoda, when rice and a plate of sugar are not given.
The merchants who visit the mine to buy, remain in their dwellings, and every morning at from 10 to 11 o’clock the masters of the miners, after they have dined (for the Banians never leave their houses till they have washed and eaten), take their diamonds to show to them. If the parcels are large, and contain many stones of the value of from 2000 up to 15000 or 16000 ecus, they entrust them to the foreign merchant for seven or eight days or more in order that he may examine them with care. When the stones have been examined, and are returned by the merchant, if they suit him he should conclude the transactions at once, otherwise the owner of the stones wraps them in a corner of his waistband, his turban, or his shirt, and departs, so that one never sees the same stones again, or at least they are mixed with others, when the miner returns with another parcel. When the transaction is concluded the purchaser gives an order for payment on the Shroff or person who issues and receives bills of exchange. If you have agreed to pay in three or four days, and delay longer, you have to pay interest at the rate of 1½ percent per month. Most frequently, when the merchant is known to be solvent, a bill of exchange on Agra, Golkonda, or Bijapur is preferred, but more especially one upon Surat, where, as it is the most famous port in India, the dealers desire to purchase the commodities which come in vessels from foreign countries, and are suitable for their wants.
Jean-Baptiste Tavernier’s Travels In India (continued)
Sunday, November 11, 2007
Singin' In The Rain
Singin' in the Rain (1952)
Directed By: Stanley Donen, Gene Kelly
Screenplay: Betty Comden, Adolph Green
Cast: Gene Kelly, Donald O'Connor, Debbie Reynolds
(via YouTube) http://www.youtube.com/watch?v=bkEvy-9yVyQ
A real gem. All-time favorite musical.
Directed By: Stanley Donen, Gene Kelly
Screenplay: Betty Comden, Adolph Green
Cast: Gene Kelly, Donald O'Connor, Debbie Reynolds
(via YouTube) http://www.youtube.com/watch?v=bkEvy-9yVyQ
A real gem. All-time favorite musical.
Nuristan
(via Wikipedia): Nuristan (also spelled Nooristan, Nurestan, or Noorestan) is one of the thirty-four provinces of Afghanistan. It was formed in 2001 from the northern parts of Laghman Province and Kunar Province. The ethnic Nuristanis make up the majority of the population of this province. Located on the southern slopes of the Hindu Kush mountains in the northeastern part of the country, Nuristan spans the basins of the Alingâr, Pech, Landai Sin, and Kunar rivers. Its capital is Nuristan. It is bordered on the north by Badakhshan Province, on the west by Panjshir Province, on the south by Laghman and Kunar provinces, and on the east by Pakistan + the region is well-known for its unique colored gemstone deposits.
Useful links:
en.wikipedia.org/wiki/Nurestan_Province
www.gems-afghan.com
Useful links:
en.wikipedia.org/wiki/Nurestan_Province
www.gems-afghan.com
MoMA Makes Its Move
Barbara Pollack writes about moving an entire museum + real-estate issues + other viewpoints @ http://artnews.com/issues/article.asp?art_id=1136
A Modernist Manifesto
Ann Landi writes about Meyer Schapiro (1904–96) + his concepts + the liberating quality of avant-garde art + other viewpoints @ http://www.artnews.com/anniversary/top4.asp
The Emerald Story
Emerald Simulants (synthetics and imitations)
Synthetic emeralds: Synthetic emeralds are man-made emeralds which have the same physical, chemical and optical properties of a natural emerald. Man has very skillfully duplicated this natural green stone so that it is sometimes extremely difficult to tell the difference. However, with the aid of magnification and other tests, a synthetic readily reveals its true identity. Synthetic emeralds have been in the market for several decades, but it’s only now, due to sophisticated mass production techniques that they have become more prevalent and a cause for concern. In the past synthetics were deceptively passed off as natural emeralds by dealers, but today they are now being successfully marketed as synthetics or lab-created by such companies as the San Francisco-based Chatham Inc, Russian-based Tairus, and others.
The techniques employed for the production of synthetic emeralds are:
- Flux growth
- Hydrothermal growth
Flux method: A flux is a chemical compound which when melted has the ability to assist another substance to melt at a temperature lower than would be normal for that material. The chemical components of emerald may be dissolved with an appropriate flux while being held within a platinum-lined crucible. Upon cooling, crystals of synthetic emerald are formed. Chatham employs the flux method for the production of his synthetic emeralds.
Typical inclusions:
- Solid masses of residual flux which appear cloudy.
- Wispy veils—look like thin veils blowing in breeze. Resemble natural liquid fingerprints, but may be more dense.
- Venetian-blind—refers to the appearance of very fine straight line growth zoning which takes on the appearance of venetian blinds.
Hydrothermal process: Of all the synthetic gem growth techniques, this process mimics most closely the process of nature for the creation of emeralds. As the name indicates, it involves water, heat and pressure. Nutrient material (chemical compound for emerald) is placed in an autoclave or ‘bomb’ along with a number of seed crystals located towards to upper (eventually cooler) part of the vessel. Heated water under high pressure dissolves the nutrient and through convection, the chemical needed to grow emerald are deposited on the seed crystal. These crystals now continue to grow so long as the conditions for growth remain and there is a supply of the nutrient.
Typical inclusions:
- Liquid feather with the appearance of fingerprints.
- Distinct fine line zoning.
- Arrow head zoning.
- Nail-head-like phenakite inclusions.
Emerald Story (continued)
Synthetic emeralds: Synthetic emeralds are man-made emeralds which have the same physical, chemical and optical properties of a natural emerald. Man has very skillfully duplicated this natural green stone so that it is sometimes extremely difficult to tell the difference. However, with the aid of magnification and other tests, a synthetic readily reveals its true identity. Synthetic emeralds have been in the market for several decades, but it’s only now, due to sophisticated mass production techniques that they have become more prevalent and a cause for concern. In the past synthetics were deceptively passed off as natural emeralds by dealers, but today they are now being successfully marketed as synthetics or lab-created by such companies as the San Francisco-based Chatham Inc, Russian-based Tairus, and others.
The techniques employed for the production of synthetic emeralds are:
- Flux growth
- Hydrothermal growth
Flux method: A flux is a chemical compound which when melted has the ability to assist another substance to melt at a temperature lower than would be normal for that material. The chemical components of emerald may be dissolved with an appropriate flux while being held within a platinum-lined crucible. Upon cooling, crystals of synthetic emerald are formed. Chatham employs the flux method for the production of his synthetic emeralds.
Typical inclusions:
- Solid masses of residual flux which appear cloudy.
- Wispy veils—look like thin veils blowing in breeze. Resemble natural liquid fingerprints, but may be more dense.
- Venetian-blind—refers to the appearance of very fine straight line growth zoning which takes on the appearance of venetian blinds.
Hydrothermal process: Of all the synthetic gem growth techniques, this process mimics most closely the process of nature for the creation of emeralds. As the name indicates, it involves water, heat and pressure. Nutrient material (chemical compound for emerald) is placed in an autoclave or ‘bomb’ along with a number of seed crystals located towards to upper (eventually cooler) part of the vessel. Heated water under high pressure dissolves the nutrient and through convection, the chemical needed to grow emerald are deposited on the seed crystal. These crystals now continue to grow so long as the conditions for growth remain and there is a supply of the nutrient.
Typical inclusions:
- Liquid feather with the appearance of fingerprints.
- Distinct fine line zoning.
- Arrow head zoning.
- Nail-head-like phenakite inclusions.
Emerald Story (continued)
Jean-Baptiste Tavernier’s Travels In India
Concerning Diamonds, And The Mines And Rivers Where They Are Found; And Especially Of The Author’s Journey To The Mine Of Rammalakota
(via Jean-Baptiste Tavernier’s Travels In India / V Ball / Edited by William Crooke)
The diamond is the most precious of all stones, and it is the article of trade to which I am most devoted. In order to acquire a thorough knowledge of it I resolved to visit all the mines, and one of the two rivers where diamonds were found; and as the fear of dangers has never restrained me in any of my journeys, the terrible picture that was drawn of these mines, situated in barbarous countries to which one could not travel except by the most dangerous routes, served neither to terrify me nor to turn me from my intention. I have accordingly been at four mines, of which I am about to give descriptions, and at one of the two rivers whence diamonds are obtained, and I have encountered there neither the difficulties nor the barbarities with which those imperfectly acquainted with the country had sought to terrify me. Thus I am able to claim that I have cleared the way for the others, and that I am the first European who has opened the route for the Franks to these mines, which are the only places in the world where the diamond is found.
The first of the mines which I visited is situated in the territory of the King of Bijapur in the Province of Carnatic, and the locality if called Rammalakota, situated five days journey from Golkonda, and eight or nine from Bijapur. The fact that the two Kings of Golkonda and Bijapur were formerly subject to the Mogul, and were then only Governors of the Provinces which they acquired by their revolt, caused it to be said, and to be still said by some people, that the diamonds come from the Empire of the Great Mogul. It is only about 200 years since this mine of Rammalakota was discovered, at least so far as I have been able to ascertain from the people of the country.
All round the place where the diamonds are found the soil is sandy, and full of rocks and jungle, somewhat comparable to the neighborhood of Fontainebleau. There are in these rocks many veins, some of half a finger and some of a whole finger in width; and the miners have small irons, crooked at the ends, which they thrust into the veins to drawn from them the sand or earth, which they place in vessels; it is in this earth that they afterwards find the diamonds. But as the veins do not always run straight, as some ascend, while others descend, they are obliged to break the rocks, always following the direction of the veins. After they have opened them out, and have removed the earth or sand which may be in them, they then commence to wash it two or three times, and search it for whatever diamonds it may contain. It is in this mine that the cleanest and whitest-watered diamonds are found; but the evil is that in order to extract the sand more easily from the rocks the miners strike such blows with a heavy iron crowbar that it fractures the diamonds, and gives rise to flaws. This is the reason why so many thin stones come from this mine, for when the miners see a stone in which there is a flaw of some size, they immediately cleave it, that is to say split it, at which they are much more accomplished than we are. These are the stones which we call thin (foible), which make a great show. If the stone is clean they do not do more than just touch it with the wheel above and below, and do not venture to give it any form, for fear of reducing the weight. But if it has a small flaw, or any spots, or small black or red grit, they cover the whole of the stone with facettes in order that its defects may not be seen, and if it has a very small flaw they conceal it by the edge of one of the facettes. But it should be remarked that the merchant prefers a black point in a stone to a red one. When there is a red one the stone is roasted, and the point becomes black. I learned this trick at length so well that when I examined a parcel of stones which came from this mine, and saw that there were facettes on any of them, especially small facettes, I was certain that there was some speck of flaw in the stone.
There are at this mine numerous diamond cutters, and each has only a steel wheel of about the size of our plates. They place but one stone on each wheel, and pour water incessantly on the wheel until they have found the ‘grain’ of the stone. The ‘grain’ being found, they pour on oil and do not spare diamond dust, although it is expensive, in order to make the stone run faster, and they weight it much more heavily than we do.
Jean-Baptiste Tavernier’s Travels In India (continued)
(via Jean-Baptiste Tavernier’s Travels In India / V Ball / Edited by William Crooke)
The diamond is the most precious of all stones, and it is the article of trade to which I am most devoted. In order to acquire a thorough knowledge of it I resolved to visit all the mines, and one of the two rivers where diamonds were found; and as the fear of dangers has never restrained me in any of my journeys, the terrible picture that was drawn of these mines, situated in barbarous countries to which one could not travel except by the most dangerous routes, served neither to terrify me nor to turn me from my intention. I have accordingly been at four mines, of which I am about to give descriptions, and at one of the two rivers whence diamonds are obtained, and I have encountered there neither the difficulties nor the barbarities with which those imperfectly acquainted with the country had sought to terrify me. Thus I am able to claim that I have cleared the way for the others, and that I am the first European who has opened the route for the Franks to these mines, which are the only places in the world where the diamond is found.
The first of the mines which I visited is situated in the territory of the King of Bijapur in the Province of Carnatic, and the locality if called Rammalakota, situated five days journey from Golkonda, and eight or nine from Bijapur. The fact that the two Kings of Golkonda and Bijapur were formerly subject to the Mogul, and were then only Governors of the Provinces which they acquired by their revolt, caused it to be said, and to be still said by some people, that the diamonds come from the Empire of the Great Mogul. It is only about 200 years since this mine of Rammalakota was discovered, at least so far as I have been able to ascertain from the people of the country.
All round the place where the diamonds are found the soil is sandy, and full of rocks and jungle, somewhat comparable to the neighborhood of Fontainebleau. There are in these rocks many veins, some of half a finger and some of a whole finger in width; and the miners have small irons, crooked at the ends, which they thrust into the veins to drawn from them the sand or earth, which they place in vessels; it is in this earth that they afterwards find the diamonds. But as the veins do not always run straight, as some ascend, while others descend, they are obliged to break the rocks, always following the direction of the veins. After they have opened them out, and have removed the earth or sand which may be in them, they then commence to wash it two or three times, and search it for whatever diamonds it may contain. It is in this mine that the cleanest and whitest-watered diamonds are found; but the evil is that in order to extract the sand more easily from the rocks the miners strike such blows with a heavy iron crowbar that it fractures the diamonds, and gives rise to flaws. This is the reason why so many thin stones come from this mine, for when the miners see a stone in which there is a flaw of some size, they immediately cleave it, that is to say split it, at which they are much more accomplished than we are. These are the stones which we call thin (foible), which make a great show. If the stone is clean they do not do more than just touch it with the wheel above and below, and do not venture to give it any form, for fear of reducing the weight. But if it has a small flaw, or any spots, or small black or red grit, they cover the whole of the stone with facettes in order that its defects may not be seen, and if it has a very small flaw they conceal it by the edge of one of the facettes. But it should be remarked that the merchant prefers a black point in a stone to a red one. When there is a red one the stone is roasted, and the point becomes black. I learned this trick at length so well that when I examined a parcel of stones which came from this mine, and saw that there were facettes on any of them, especially small facettes, I was certain that there was some speck of flaw in the stone.
There are at this mine numerous diamond cutters, and each has only a steel wheel of about the size of our plates. They place but one stone on each wheel, and pour water incessantly on the wheel until they have found the ‘grain’ of the stone. The ‘grain’ being found, they pour on oil and do not spare diamond dust, although it is expensive, in order to make the stone run faster, and they weight it much more heavily than we do.
Jean-Baptiste Tavernier’s Travels In India (continued)
Spain Shown Perils Of Climate Change
(via The Guardian) The images from the book 'Photoclima' via Greenpeace is quite shocking. What will be the fate of cities like Dubai, Singapore, and other coastal cities in the coming decades? Frightening and nowhere to run!
Useful link:
http://www.guardian.co.uk/environment/2007/nov/10/flooding.climatechange
Useful link:
http://www.guardian.co.uk/environment/2007/nov/10/flooding.climatechange
Madagascar
(via Wikipedia) Madagascar, or Republic of Madagascar (older name Malagasy Republic), is an island nation in the Indian Ocean off the southeastern coast of Africa. The main island, also called Madagascar, is the fourth largest island in the world, and is home to five percent of the world's plant and animal species; more than 80 percent of which are endemic to Madagascar. Most notable are the lemur infraorder of primates, the carnivorous fossa, three endemic bird families and six endemic baobab species + the entire country is rich in colored gemstones.
Useful links:
http://en.wikipedia.org/wiki/Madagascar
http://www.lonelyplanet.com/worldguide/destinations/africa/madagascar
Useful links:
http://en.wikipedia.org/wiki/Madagascar
http://www.lonelyplanet.com/worldguide/destinations/africa/madagascar
Enrico Caruso
Enrico Caruso was an Italian opera singer + one of the most famous tenors in history. I enjoy the music + listening to Caruso's songs + his extraordinary voice + the natural tone is inspirational and therapeutic. He was a superstar of his time but the music still lives on.
Enrico Caruso songs:
La donna è mobile
Ave Maria
Vesti La Giubba
No Pagliaccio non son
La Partida
O Sole Mio
Santa Lucia
(via Henry Rosner) Hear Enrico Caruso sing Vesti la giubba from "I Pagliacci, Act 1" 17 March 1907 (in mp3 format)
More information about Enrico Caruso's recordings @ Enrico Caruso recordings.
Enrico Caruso songs:
La donna è mobile
Ave Maria
Vesti La Giubba
No Pagliaccio non son
La Partida
O Sole Mio
Santa Lucia
(via Henry Rosner) Hear Enrico Caruso sing Vesti la giubba from "I Pagliacci, Act 1" 17 March 1907 (in mp3 format)
More information about Enrico Caruso's recordings @ Enrico Caruso recordings.
Saturday, November 10, 2007
The Emerald Story
The main cuts employed for emeralds
Step/Emerald cut: This is the most important and popular cut employed for emeralds. All facets are cut in squares or rectangles which are arranged in steps, giving an elongated octagonal outline. The best quality emeralds are almost universally fashioned in this way for these reasons:
- It shows the saturated deep velvety-green of emerald to the best advantage. Since color is the most important determinant of value in emeralds, a stone with a good depth of color fetches a higher market price than one that does not.
- The step cut minimizes loss of mass during cutting and polishing. This means more carat weight retention of the stone and hence value (value = price/carat x carat weight).
Mixed cut: The crown of the stone is brilliant cut, while the pavilion is step cut. It is not very popular since it gives the stone a pale glassy look, which is not desirable.
Cabochon & beads: Stones which are turbid and heavily included and are of good color are commonly cut as cabochons and beads. A cabochon may have a flat base and a dome-shaped upper portion. Emeralds cut in this manner are usually sub-transparent to opaque, and can range from light to very dark green. Emeralds of low to medium quality are thus fashioned. Emerald beads and cabochons are becoming increasingly popular since they are a beautiful yet inexpensive form of natural emeralds.
Fancy cuts and carvings: Heavily included emeralds with good color but limited transparency are an excellent base for carving. Carved emeralds are fashioned into pendants, belt-buckles, and show pieces in a variety of exotic jewelry.
The cut of a stone is crucial to its color and beauty, and has great influence on its ultimate value.
Common treatments applied to emeralds
Mining, cutting, faceting, and polishing procedures are accepted and considered, as the normal processing of gemstones. However, in his endeavor to enhance value, man has subjected his gems to further treatments. Some of the treatments are necessary and are now accepted as normal processing for a gemstone, while others are subject to disclosure.
The common treatments for emeralds are oiling, staining/dyeing and resin impregnation.
Oiling: Perhaps the most universal treatment for emeralds, practised by emerald dealers all over the world. This treatment is more of a finishing touch applied to emeralds of good color but with visible internal fissures. Oiling enhances surface shine and luster, and reduces the visibility of fissures in the stone, thereby adding to its saleability.
Oils used: Cedarwood oil, Canada Balsam, mineral oil.
Method: The method of oiling varies from dealer to dealer, with much being kept secret for obvious reasons. But basically, it involves these steps: (a) Emeralds are first cleaned thoroughly using a mild acid (b) They are then soaked in warm clear oil (Cedar oil is popular) and subjected to appropriate heat and sometimes pressure or vacuum.
Effect: The oil permeates into the fissures and fills them, reducing their visibility. Modern oiling machines offer an easily and effective treatment method for emeralds.
Durability of treatment: The oil comes out of the fissures when subjected to heat, ultrasonic cleansing, immersion in soapy water or acids, alcohol or other solvents. Otherwise, for normal wear and tear, it remains stable for a reasonable period of time. Stones can be re-oiled if necessary.
The practice of oiling is so prevalent that it is hard to curb. It is regarded as standard practice. But since the effect is not 100% permanent, trade organizations and gem testing laboratories encourages disclosure of the treatment to customers upon purchase.
Detection of oiling under the microscope: Traces of oil may be seen in fissures when the stone is viewed under the microscope. Typical signs of oiling are:
- Low relief of fissures that would otherwise appear white. Some fissures tend to appear shiny (fluid-like) when viewed at certain angles.
- Flattened gas bubbles trapped in the filling media (oil)
- Some oils fluoresce (emit light) when subjected to ultra-violet (UV) radiation. For e.g. Canada Balsam shows a weak greenish yellow light under UV.
Staining/dyeing: Yet another age-old technique to enhance the appearance of a gem that is commonly applied to emeralds. Whereas the main motive for oiling an emerald is to conceal fissures, the main aim of dyeing an emerald is to give a false appearance of color in otherwise pale-colored emeralds. The dyeing of colorless beryl to simulate the appearance of emerald is also carried out. Staining or dyeing may be either a surface only treatment or it may penetrate fissures.
Dyes used: Natural organic dyes, synthetic dyes (e.g. aniline) compounds of metallic salts.
Method: (a) The stone is thoroughly cleaned. (b) The stone is soaked in oil containing the green dye at an appropriate temperature for a few hours.
Effect: The green oil permeates into the stone increasing depth of color, and reducing the visibility of internal fissures.
Durability of treatment: Natural organic dyes are least stable and some deteriorate easily. Synthetic dyes tend to last longer. Certain dyes don’t come out of the fissures even if the oil wears off when subject to heat or alcohol.
Status of treatment: Since dyeing significantly alters the appearance of emeralds and possibly other beryls and is not permanent, this treatment should be disclosed to customers upon purchase.
Detection of treatment: One can always detect the presence of dye under magnification. Indications are: (a) Color concentration in fissures and chips, (b) Slightly colored outlining of fissures, (c) Uneven color distribution, (d) Some colored oils fluoresce under UV radiation.
Resin impregnation of fissures (Opticon treatment): A relatively recent development in the treatment of emeralds. It involves impregnating fissures with a synthetic resin marketed as Opticon. Opticon, as a resin, is more durable than oil, making the treatment more permanent. It is a two part product consisting of the resin itself plus a separate hardener (an additional fluid which when added to the resin causes it to become hard). A vacuum is usually used to assist the flow of the resin into the fissures in emerald. Sometimes the treater will then add the hardener and sometimes not.
Detection of the treatment: Many resins, including Opticon can be detected by the observation of blue and yellow/orange color flashes coming from the region of treated fissures. Positive identification can come from Raman spectroscopy available only in the best equipped gem labs.
Status of treatment: If no hardener is applied, whilst this resin treatment might be a little more stable than oiling it is still not permanent. If a hardener is applied this may cause fissures to expand under warm conditions, or when being repolished, which may result in severe damage-occurring. Hence, disclosure of treatment is required.
Emerald Story (continued)
Step/Emerald cut: This is the most important and popular cut employed for emeralds. All facets are cut in squares or rectangles which are arranged in steps, giving an elongated octagonal outline. The best quality emeralds are almost universally fashioned in this way for these reasons:
- It shows the saturated deep velvety-green of emerald to the best advantage. Since color is the most important determinant of value in emeralds, a stone with a good depth of color fetches a higher market price than one that does not.
- The step cut minimizes loss of mass during cutting and polishing. This means more carat weight retention of the stone and hence value (value = price/carat x carat weight).
Mixed cut: The crown of the stone is brilliant cut, while the pavilion is step cut. It is not very popular since it gives the stone a pale glassy look, which is not desirable.
Cabochon & beads: Stones which are turbid and heavily included and are of good color are commonly cut as cabochons and beads. A cabochon may have a flat base and a dome-shaped upper portion. Emeralds cut in this manner are usually sub-transparent to opaque, and can range from light to very dark green. Emeralds of low to medium quality are thus fashioned. Emerald beads and cabochons are becoming increasingly popular since they are a beautiful yet inexpensive form of natural emeralds.
Fancy cuts and carvings: Heavily included emeralds with good color but limited transparency are an excellent base for carving. Carved emeralds are fashioned into pendants, belt-buckles, and show pieces in a variety of exotic jewelry.
The cut of a stone is crucial to its color and beauty, and has great influence on its ultimate value.
Common treatments applied to emeralds
Mining, cutting, faceting, and polishing procedures are accepted and considered, as the normal processing of gemstones. However, in his endeavor to enhance value, man has subjected his gems to further treatments. Some of the treatments are necessary and are now accepted as normal processing for a gemstone, while others are subject to disclosure.
The common treatments for emeralds are oiling, staining/dyeing and resin impregnation.
Oiling: Perhaps the most universal treatment for emeralds, practised by emerald dealers all over the world. This treatment is more of a finishing touch applied to emeralds of good color but with visible internal fissures. Oiling enhances surface shine and luster, and reduces the visibility of fissures in the stone, thereby adding to its saleability.
Oils used: Cedarwood oil, Canada Balsam, mineral oil.
Method: The method of oiling varies from dealer to dealer, with much being kept secret for obvious reasons. But basically, it involves these steps: (a) Emeralds are first cleaned thoroughly using a mild acid (b) They are then soaked in warm clear oil (Cedar oil is popular) and subjected to appropriate heat and sometimes pressure or vacuum.
Effect: The oil permeates into the fissures and fills them, reducing their visibility. Modern oiling machines offer an easily and effective treatment method for emeralds.
Durability of treatment: The oil comes out of the fissures when subjected to heat, ultrasonic cleansing, immersion in soapy water or acids, alcohol or other solvents. Otherwise, for normal wear and tear, it remains stable for a reasonable period of time. Stones can be re-oiled if necessary.
The practice of oiling is so prevalent that it is hard to curb. It is regarded as standard practice. But since the effect is not 100% permanent, trade organizations and gem testing laboratories encourages disclosure of the treatment to customers upon purchase.
Detection of oiling under the microscope: Traces of oil may be seen in fissures when the stone is viewed under the microscope. Typical signs of oiling are:
- Low relief of fissures that would otherwise appear white. Some fissures tend to appear shiny (fluid-like) when viewed at certain angles.
- Flattened gas bubbles trapped in the filling media (oil)
- Some oils fluoresce (emit light) when subjected to ultra-violet (UV) radiation. For e.g. Canada Balsam shows a weak greenish yellow light under UV.
Staining/dyeing: Yet another age-old technique to enhance the appearance of a gem that is commonly applied to emeralds. Whereas the main motive for oiling an emerald is to conceal fissures, the main aim of dyeing an emerald is to give a false appearance of color in otherwise pale-colored emeralds. The dyeing of colorless beryl to simulate the appearance of emerald is also carried out. Staining or dyeing may be either a surface only treatment or it may penetrate fissures.
Dyes used: Natural organic dyes, synthetic dyes (e.g. aniline) compounds of metallic salts.
Method: (a) The stone is thoroughly cleaned. (b) The stone is soaked in oil containing the green dye at an appropriate temperature for a few hours.
Effect: The green oil permeates into the stone increasing depth of color, and reducing the visibility of internal fissures.
Durability of treatment: Natural organic dyes are least stable and some deteriorate easily. Synthetic dyes tend to last longer. Certain dyes don’t come out of the fissures even if the oil wears off when subject to heat or alcohol.
Status of treatment: Since dyeing significantly alters the appearance of emeralds and possibly other beryls and is not permanent, this treatment should be disclosed to customers upon purchase.
Detection of treatment: One can always detect the presence of dye under magnification. Indications are: (a) Color concentration in fissures and chips, (b) Slightly colored outlining of fissures, (c) Uneven color distribution, (d) Some colored oils fluoresce under UV radiation.
Resin impregnation of fissures (Opticon treatment): A relatively recent development in the treatment of emeralds. It involves impregnating fissures with a synthetic resin marketed as Opticon. Opticon, as a resin, is more durable than oil, making the treatment more permanent. It is a two part product consisting of the resin itself plus a separate hardener (an additional fluid which when added to the resin causes it to become hard). A vacuum is usually used to assist the flow of the resin into the fissures in emerald. Sometimes the treater will then add the hardener and sometimes not.
Detection of the treatment: Many resins, including Opticon can be detected by the observation of blue and yellow/orange color flashes coming from the region of treated fissures. Positive identification can come from Raman spectroscopy available only in the best equipped gem labs.
Status of treatment: If no hardener is applied, whilst this resin treatment might be a little more stable than oiling it is still not permanent. If a hardener is applied this may cause fissures to expand under warm conditions, or when being repolished, which may result in severe damage-occurring. Hence, disclosure of treatment is required.
Emerald Story (continued)
Memories Of Spain
(via The Guardian) James Fenton writes about the Hispanic Society of America, on West 155th Street in Manhattan (USA) + Archer Milton Huntington + his passion + other viewpoints @ http://arts.guardian.co.uk/art/visualart/story/0,,2204239,00.html
The Real Thing?
Ann Landi writes about contemporary realism + handful of mature artists pursuing realist idiom of one stripe or another + the impact + other viewpoints @ http://artnews.com/issues/article.asp?art_id=1150
The Burgundian Point Cut
(via Diamond Cuts in Historic Jewelry:1381-1910) Herbert Tillander writes:
A Refined Dodecahedron
In the days when superstition prevailed, a cutter could evade the strict rules which controlled the shapes of fashioned diamonds if he had a particularly well developed dodecahedron at his disposal. The four rhombic faces of such a crystal, chosen to face the viewer, could be smoothed and polished at a minimal angle of inclination, thus preserving the shape of a natural crystal.
Crystals fashioned in this way, side by side with Pyramidal Points and Table Cuts, were entirely acceptable and considered ideal as talismans. The Court Goblet of the Duchy of Burgundy in the Vienna Hofburg, with its numerous early and mid-fifteenth century diamonds, is our foremost source of information on cuts of the period. It also indicates that fashioning had been fully mastered by then.
The majority of the larger diamonds display brilliance in the modern sense of the term. This means that by the early fifteenth century cutters had discovered the property inherent in diamonds of reflecting the rays of light from pavilion facets set at correct angles of inclination. Fortunately for posterity, princes of refined taste appreciated these sparkling qualities of diamonds, although at the time fashion still demanded pyramidal shapes and Table Cuts, disapproving of brilliance.
The Burgundian is also exceptional in that it became a prototype which could, simply by means of additional faceting, be transformed into a number of other patterns: the Pointed Star, the Taille en Seize, and finally the Baroque type of Brilliant cut. It was also economical, since it could be fashioned on the wheel alone, and therefore with comparatively little loss of weight.
At first, the pavilion did not differ very much from the crown, but when strictly crystal-like shapes were no longer challenged, the cutters were free to fashion the pavilions differently—depending, of course, on the symmetry of the crystal and the presence of disturbing inclusions in the lower part of the gem.
As a rule, natural dodecahedrons have distinctly rounded faces and sharp, curved edges. Symmetrization of these faces presented no problems to the cutters. The corners were frequently left blunt and were partly hidden by the setting, so that regular crystals could be made to appear almost perfectly round or oval or lozenge-shaped. They were about 25 per cent lower than Pyramidal Point Cuts, but looked lower still because of their semi-spherical appearance. In addition to an amazing amount of brilliance, many of the fashioned gems also displayed fire. Easily identified in contemporary inventories, they are frequently described as having four main lozenge-shaped facets in the center, surrounded by eight semi-lozenges—i.e. Lozenges split into two triangles. In many cases they are described simply as faceted diamonds with an adjective indicating the outline.
As the fashion for Table Cuts (both traditional and more exotically faceted) grew, the apexes of many Burgundian Cuts were ground down. Later, most of the remaining stones of this type were re-cut, the larger sizes into Baroque Brilliants and some smaller ones into matching complementary Double Cuts. This explains why so few Burgundian Point Cuts have survived in their original form.
Fortunately, there are two on the Burgundian Court Goblet. The larger gem, which is about 8.7 mm in diameter, is in a separate setting. In 1621 it was described as ‘Ain Diamant spitzig sternweiss geschnitten (a pointed diamond cut like a star)’. The smaller gem, about 5 x 3 mm in size, forms part of a fleur-de-lis.
An illustration by an artist from Basel, drawn in about 1500, shows a Burgandian Cut on another famous jewel belonging to Charles the Bold, the Feather, thought to have been made in the 1460s. The stone, which must have been about 12.5 mm in diameter, with a weight of about 6 ct, can be seen very clearly in the sales document drawn up between the City of Basel and Fugger’s, and was described as ‘ein demant mit faceten, gutt wasser, nit rein, vol swartzer bunten’.
There is one other illustration of a jewel covered with diamonds of this type. This is a sketch drawn, according to Erna von Watzdorf, by G.C Dinglinger, the less talented brother of the famous Johann Melchior Dinglinger. The drawing is said to date from as late as 1719, when this type of cut was already out of fashion.
A Refined Dodecahedron
In the days when superstition prevailed, a cutter could evade the strict rules which controlled the shapes of fashioned diamonds if he had a particularly well developed dodecahedron at his disposal. The four rhombic faces of such a crystal, chosen to face the viewer, could be smoothed and polished at a minimal angle of inclination, thus preserving the shape of a natural crystal.
Crystals fashioned in this way, side by side with Pyramidal Points and Table Cuts, were entirely acceptable and considered ideal as talismans. The Court Goblet of the Duchy of Burgundy in the Vienna Hofburg, with its numerous early and mid-fifteenth century diamonds, is our foremost source of information on cuts of the period. It also indicates that fashioning had been fully mastered by then.
The majority of the larger diamonds display brilliance in the modern sense of the term. This means that by the early fifteenth century cutters had discovered the property inherent in diamonds of reflecting the rays of light from pavilion facets set at correct angles of inclination. Fortunately for posterity, princes of refined taste appreciated these sparkling qualities of diamonds, although at the time fashion still demanded pyramidal shapes and Table Cuts, disapproving of brilliance.
The Burgundian is also exceptional in that it became a prototype which could, simply by means of additional faceting, be transformed into a number of other patterns: the Pointed Star, the Taille en Seize, and finally the Baroque type of Brilliant cut. It was also economical, since it could be fashioned on the wheel alone, and therefore with comparatively little loss of weight.
At first, the pavilion did not differ very much from the crown, but when strictly crystal-like shapes were no longer challenged, the cutters were free to fashion the pavilions differently—depending, of course, on the symmetry of the crystal and the presence of disturbing inclusions in the lower part of the gem.
As a rule, natural dodecahedrons have distinctly rounded faces and sharp, curved edges. Symmetrization of these faces presented no problems to the cutters. The corners were frequently left blunt and were partly hidden by the setting, so that regular crystals could be made to appear almost perfectly round or oval or lozenge-shaped. They were about 25 per cent lower than Pyramidal Point Cuts, but looked lower still because of their semi-spherical appearance. In addition to an amazing amount of brilliance, many of the fashioned gems also displayed fire. Easily identified in contemporary inventories, they are frequently described as having four main lozenge-shaped facets in the center, surrounded by eight semi-lozenges—i.e. Lozenges split into two triangles. In many cases they are described simply as faceted diamonds with an adjective indicating the outline.
As the fashion for Table Cuts (both traditional and more exotically faceted) grew, the apexes of many Burgundian Cuts were ground down. Later, most of the remaining stones of this type were re-cut, the larger sizes into Baroque Brilliants and some smaller ones into matching complementary Double Cuts. This explains why so few Burgundian Point Cuts have survived in their original form.
Fortunately, there are two on the Burgundian Court Goblet. The larger gem, which is about 8.7 mm in diameter, is in a separate setting. In 1621 it was described as ‘Ain Diamant spitzig sternweiss geschnitten (a pointed diamond cut like a star)’. The smaller gem, about 5 x 3 mm in size, forms part of a fleur-de-lis.
An illustration by an artist from Basel, drawn in about 1500, shows a Burgandian Cut on another famous jewel belonging to Charles the Bold, the Feather, thought to have been made in the 1460s. The stone, which must have been about 12.5 mm in diameter, with a weight of about 6 ct, can be seen very clearly in the sales document drawn up between the City of Basel and Fugger’s, and was described as ‘ein demant mit faceten, gutt wasser, nit rein, vol swartzer bunten’.
There is one other illustration of a jewel covered with diamonds of this type. This is a sketch drawn, according to Erna von Watzdorf, by G.C Dinglinger, the less talented brother of the famous Johann Melchior Dinglinger. The drawing is said to date from as late as 1719, when this type of cut was already out of fashion.
An Engagement And Wedding Web Site For Men
Groomgroove.com, an engagement and wedding web site for men is an interesting concept + the calculator allows the groom to enter his gross salary + calculate what he should spend on a diamond engagement ring + provides information for the groom-to-be on how to buy an engagement ring + other infos.
A brilliant idea.
A brilliant idea.
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