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.

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

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)

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.

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

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)