Friday, November 02, 2007
Mali's Diamond-smuggling Centre
(via BBC Network Africa): Celeste Hicks writes about Mali's south-eastern town of Sikasso + the diamond smuggling network + other viewpoints @ http://news.bbc.co.uk/2/hi/africa/7071286.stm
(via FastCompany) Ellen McGirt writes about Facebook + the new business applications + building ecosystems that's business/user-friendly + other viewpoints @ Facebook is the "It" Company of 2007.
Useful link:
http://www.fastcompany.com/magazine/120/facebook-is-the-it-company-of-2007.html
Useful link:
http://www.fastcompany.com/magazine/120/facebook-is-the-it-company-of-2007.html
Museum Of Broken Relationships Opens
(via The Guardian) Kate Connolly writes about an interesting outlet for painful experiences - The Museum of Broken Relationships + other viewpoints @ http://arts.guardian.co.uk/art/news/story/0,,2201097,00.html
HINT: Avoid The Word ‘Nice’
Paul Gardner writes about the do's and dont's at art opening (s) + other viewpoints @ http://artnews.com/issues/article.asp?art_id=1437
Zambia And Gemstones
(via YouTube): Loose Gemstone Mining in Zambia, Africa
http://www.youtube.com/watch?v=hqybLjT5huM
It was educational.
http://www.youtube.com/watch?v=hqybLjT5huM
It was educational.
Roman Jewelers And Lapidaries
(via Roman Book On Precious Stones: 1950) Sydney H Ball writes:
Among the engravers’ tools were diamond splinters, set in iron, capable of cutting the hardest substances known: for softer stones emery or merely an iron point were used by engravers. The gem engraver also used the lima (or file) and in the bronze statue which Theodorus of Samos, architect, sculptor, and gem engraver, cast of himself, he holds a file in his right hand. He was one of the earliest gem engravers known, being mentioned by Herodotus. The file consisted of a mixture of emery and melted resin. Appuleius says that Hippias, the philosopher, used one in engraving the gem set in a ring which he fabricated for himself. Maecenas in a letter to Horace also mentions the lima. This is the forerunner of the diamond impregnated wheels and tools of today. The lapidary’s wheel with its accompanying drills was used by the Mesopotamian lapidaries in the 4th millenieum before Christ and reached Europe between 1800 and 1600 B.C (Minoan III period). The gravestone of a gem cutter found at Philadelphia, Asia Minor, in a broad way a contemporary of Pliny, shows what appears to be a bow drill. Doubtless some of the diamond splinters set in iron were used as tools in such drills. A Greek gem of the 5th century B.C now in the British Museum, also shows drilling. The Greek name for this type of artist, dacyloiloglyphos, is most descriptive, ‘he whose fingers hollow out the stone.’ The Roman lapidary also used a saw (serra) consisting of a wire drawn back and forth, fed with a powdered abrasive. The ostracious (perhaps flint) was also used to engrave gems. Whether the gem engraver used a magnifying glass is a moot question.
At first the worker in gold was called aurarius, later aurifex, and the retailer of rings, anularii. As to the setting of gems, Pliny says little. The beauty of the turquoise is, however, heightened by setting in gold, the contrast of the stone and the gold being admirable: a statement true today. The chrysolithos (topaz) if fine was set a jour in an open bezel, if of inferior quality its color was heightened by a foil of aurichalcium (a copper compound). The beauty of sarda (our carnelian) was, in some instances, increased by the use of silver foil and in others of gold. The art of the use of foils is an old one. The Minoans (2000-1600 B.C) made a gaming table decorated with strips and discs of rich crystal. The latter was alternately backed by silver plaques and blue vitreous paste (cyanos).
The Roman private banker, like the bankers of the Middle Ages, traded in precious metals and stones and usually also performed the functions of a dealer in gold and silverware. The Roman merchant was a greater traveler than his American confrere, a personal interview being required in many instances in which today a letter, a telephone call, a telegram, or a radio message suffices.
Like the people of the East, each trade in Rome tended to have its quarters. In 211 B.C, Hannibal was much annoyed when he pitched his camp on the Anio and found that in Rome the very land on which his tent was standing had since then been sold in Rome, with no reduction in price, so Livy tells us. Being at the city walls, he was so confident of the city’s fall that ‘in pique he bade an auctioneer put up the silversmith’s shops in the Forum for sale.’ The finest jewelry shops in Pliny’s time were in the great market buildings by the Saepta Julia on the Campus Martius, on the Porticus Argonautorum and the Via Sacra. On these Fifth Avenues of ancient Rome, one could purchase crystal cups, agate vases, and jewelry of every sort. We obtain an idea of the shops themselves from Martial, who describes Mamurra, a fourflusher, on a shopping tour in Rome. He examined everything. Next, complaining that some crystal vases had been spoiled by admixture of glass, he selected and set aside ten murrhine cups. He counted emeralds set in chased gold, and examined the largest pearl ear pendants. He sought on every counter for real sardonyxes and cheapened some large jaspers. At last when forced by fatigue to retire at the eleventh hour, he bought two cups for one small coin and carried them home himself. Many inscriptions have been found on the Via Sacra relating to tradesmen in luxuries, particularly jewelers. While the jewelers, engravers of gems, and lapidaries had workshops on the Via Sacra, much jewelry was imported from Asia Minor and from Alexandria, Egypt, while at least some of the cups of precious stones were cut in the East. Certain provincial towns were noted for their precious wares, Aquileia, for example, for its amber object d’art, its silverware, and its gold jewelry. Some twenty years ago there was excavated in the Via dell’ Abbondanza, Pompeii, the house of one Cerialis, a jeweler of Pliny’s time. In his flight from the terrors of the eruption he doubtless took with him his finest gems but a number of precious stones and some tools were left behind in his shop. In the dining room of the house of the Vettii in Pompeii is a most amusing mural depicting all phases of the jewelry trade. The proprietor, the artisans, and the grande dame client are all cherubs, entrancingly chubby, their absurdly small wings apparently too short for long distance flight.
Roman Jewelers And Lapidaries (continued)
Among the engravers’ tools were diamond splinters, set in iron, capable of cutting the hardest substances known: for softer stones emery or merely an iron point were used by engravers. The gem engraver also used the lima (or file) and in the bronze statue which Theodorus of Samos, architect, sculptor, and gem engraver, cast of himself, he holds a file in his right hand. He was one of the earliest gem engravers known, being mentioned by Herodotus. The file consisted of a mixture of emery and melted resin. Appuleius says that Hippias, the philosopher, used one in engraving the gem set in a ring which he fabricated for himself. Maecenas in a letter to Horace also mentions the lima. This is the forerunner of the diamond impregnated wheels and tools of today. The lapidary’s wheel with its accompanying drills was used by the Mesopotamian lapidaries in the 4th millenieum before Christ and reached Europe between 1800 and 1600 B.C (Minoan III period). The gravestone of a gem cutter found at Philadelphia, Asia Minor, in a broad way a contemporary of Pliny, shows what appears to be a bow drill. Doubtless some of the diamond splinters set in iron were used as tools in such drills. A Greek gem of the 5th century B.C now in the British Museum, also shows drilling. The Greek name for this type of artist, dacyloiloglyphos, is most descriptive, ‘he whose fingers hollow out the stone.’ The Roman lapidary also used a saw (serra) consisting of a wire drawn back and forth, fed with a powdered abrasive. The ostracious (perhaps flint) was also used to engrave gems. Whether the gem engraver used a magnifying glass is a moot question.
At first the worker in gold was called aurarius, later aurifex, and the retailer of rings, anularii. As to the setting of gems, Pliny says little. The beauty of the turquoise is, however, heightened by setting in gold, the contrast of the stone and the gold being admirable: a statement true today. The chrysolithos (topaz) if fine was set a jour in an open bezel, if of inferior quality its color was heightened by a foil of aurichalcium (a copper compound). The beauty of sarda (our carnelian) was, in some instances, increased by the use of silver foil and in others of gold. The art of the use of foils is an old one. The Minoans (2000-1600 B.C) made a gaming table decorated with strips and discs of rich crystal. The latter was alternately backed by silver plaques and blue vitreous paste (cyanos).
The Roman private banker, like the bankers of the Middle Ages, traded in precious metals and stones and usually also performed the functions of a dealer in gold and silverware. The Roman merchant was a greater traveler than his American confrere, a personal interview being required in many instances in which today a letter, a telephone call, a telegram, or a radio message suffices.
Like the people of the East, each trade in Rome tended to have its quarters. In 211 B.C, Hannibal was much annoyed when he pitched his camp on the Anio and found that in Rome the very land on which his tent was standing had since then been sold in Rome, with no reduction in price, so Livy tells us. Being at the city walls, he was so confident of the city’s fall that ‘in pique he bade an auctioneer put up the silversmith’s shops in the Forum for sale.’ The finest jewelry shops in Pliny’s time were in the great market buildings by the Saepta Julia on the Campus Martius, on the Porticus Argonautorum and the Via Sacra. On these Fifth Avenues of ancient Rome, one could purchase crystal cups, agate vases, and jewelry of every sort. We obtain an idea of the shops themselves from Martial, who describes Mamurra, a fourflusher, on a shopping tour in Rome. He examined everything. Next, complaining that some crystal vases had been spoiled by admixture of glass, he selected and set aside ten murrhine cups. He counted emeralds set in chased gold, and examined the largest pearl ear pendants. He sought on every counter for real sardonyxes and cheapened some large jaspers. At last when forced by fatigue to retire at the eleventh hour, he bought two cups for one small coin and carried them home himself. Many inscriptions have been found on the Via Sacra relating to tradesmen in luxuries, particularly jewelers. While the jewelers, engravers of gems, and lapidaries had workshops on the Via Sacra, much jewelry was imported from Asia Minor and from Alexandria, Egypt, while at least some of the cups of precious stones were cut in the East. Certain provincial towns were noted for their precious wares, Aquileia, for example, for its amber object d’art, its silverware, and its gold jewelry. Some twenty years ago there was excavated in the Via dell’ Abbondanza, Pompeii, the house of one Cerialis, a jeweler of Pliny’s time. In his flight from the terrors of the eruption he doubtless took with him his finest gems but a number of precious stones and some tools were left behind in his shop. In the dining room of the house of the Vettii in Pompeii is a most amusing mural depicting all phases of the jewelry trade. The proprietor, the artisans, and the grande dame client are all cherubs, entrancingly chubby, their absurdly small wings apparently too short for long distance flight.
Roman Jewelers And Lapidaries (continued)
Emerald Story
Historical significance
Emeralds are green gemstones colored by a trace of chromium, which belong to the mineral species called beryl. The name emerald is derived from the Greek word Smaragdos which in turn was derived from a Persian word. However, Smaragdos referred to all green gemstones at that time.
An interesting historical fact about emerald is that it was considered the symbol of immortality and faith, and was dedicated by the ancients to the goddess of love—Venus. It is even said to be beneficial to the eyes (this may be related to the fact that green in general has a nice soothing effect on the eyes). The greenery around us also helps to refresh our eyes.
Physical and Chemical properties of Emerald
Color: Emerald green, light green, bluish green, yellowish green and dark green.
Moh’s hardness: 7.5 Moh’s hardness measure’s a gemstone’s resistance to surface scratches. Gemstones with a hardness of above 7 are reasonably resistant to surface scratches, making them more durable. Durability is one of the most important attributes of a gemstone.
Specific gravity: 2.7-2.8. The specific gravity (SG) compares the weight of a gemstone with the weight of an equal volume of water at 4ºC. This means that emerald is approximately 2.7 times heavier than an equal volume of water at 4ºC.
Transparency: Transparent to opaque.
Refractive index: 1.57-1.59 (DR=0.006-0.008). The R.I of a gemstone compares the speed of light in air to the speed of light in the gemstone. The R.I of a stone can be measured with the refractometer.
Chemical composition: Al2Be3(SiO3)6 Aluminum beryllium silicate. The green color is imparted due to the presence of chromium and traces of iron darker this color.
Typical inclusions: Emeralds are characterized by inclusions such as liquid filled cavities, liquid filled cavities with gas bubbles (2-phase), liquid-filled cavities with gas bubbles and solid crystals (3-phase), solid inclusions such pyrite and calcite, surface reaching fissures and fissures often containing oil or resin, cloudy patches with liquid fingerprint inclusions. To the gemologist inclusions are regarded as flaws, but are evidence to the authenticity, or otherwise, of the stone. They also lend a unique exotic appeal to the stone, and have often been referred to as a jardin (or the emerald’s garden) by the experts.
Emerald formation and mining methods
Emerald belongs to the mineral species called beryl. Beryl in its pure form is colorless. When it acquires a green color owing to the presence of traces of chromium it is called emerald. Blue colored beryl is called aquamarine, pink color (less common) is called morganite, yellow is heliodor. Emerald (and other beryl) crystals mostly form within a hydrothermal environment when the elements, aluminum, beryllium and silica are present in the ideal amounts and combine in a chemical reaction to form crystals of beryl. When chromium is present the crystals acquire the rich green color of emerald. Beryl crystals are found within veins and embedded in the host rocks.
Mining methods
The mining methods employed for emeralds is still rather primitive. The tools commonly used are hand chisels, sickles, sticks and hammers to procure the stone from the host rock. Explosives are only used when absolutely necessary due to the very real danger such a practice might have on any fine (and valuable) crystals.
Two main mining methods are employed:
- Shaft mining / tunnel mining: Shafts and / or tunnels are dug in the ground and the gems procured.
- Terrace mining: Emerald bearing veins are exposed by digging horizontal terraces in step-like formation along gullies. The surrounding debris is washed away with water released from a lake like reservoir above the cuttings. The emeralds thus procured are washed and sorted into parcels.
Emerald (continued)
Emeralds are green gemstones colored by a trace of chromium, which belong to the mineral species called beryl. The name emerald is derived from the Greek word Smaragdos which in turn was derived from a Persian word. However, Smaragdos referred to all green gemstones at that time.
An interesting historical fact about emerald is that it was considered the symbol of immortality and faith, and was dedicated by the ancients to the goddess of love—Venus. It is even said to be beneficial to the eyes (this may be related to the fact that green in general has a nice soothing effect on the eyes). The greenery around us also helps to refresh our eyes.
Physical and Chemical properties of Emerald
Color: Emerald green, light green, bluish green, yellowish green and dark green.
Moh’s hardness: 7.5 Moh’s hardness measure’s a gemstone’s resistance to surface scratches. Gemstones with a hardness of above 7 are reasonably resistant to surface scratches, making them more durable. Durability is one of the most important attributes of a gemstone.
Specific gravity: 2.7-2.8. The specific gravity (SG) compares the weight of a gemstone with the weight of an equal volume of water at 4ºC. This means that emerald is approximately 2.7 times heavier than an equal volume of water at 4ºC.
Transparency: Transparent to opaque.
Refractive index: 1.57-1.59 (DR=0.006-0.008). The R.I of a gemstone compares the speed of light in air to the speed of light in the gemstone. The R.I of a stone can be measured with the refractometer.
Chemical composition: Al2Be3(SiO3)6 Aluminum beryllium silicate. The green color is imparted due to the presence of chromium and traces of iron darker this color.
Typical inclusions: Emeralds are characterized by inclusions such as liquid filled cavities, liquid filled cavities with gas bubbles (2-phase), liquid-filled cavities with gas bubbles and solid crystals (3-phase), solid inclusions such pyrite and calcite, surface reaching fissures and fissures often containing oil or resin, cloudy patches with liquid fingerprint inclusions. To the gemologist inclusions are regarded as flaws, but are evidence to the authenticity, or otherwise, of the stone. They also lend a unique exotic appeal to the stone, and have often been referred to as a jardin (or the emerald’s garden) by the experts.
Emerald formation and mining methods
Emerald belongs to the mineral species called beryl. Beryl in its pure form is colorless. When it acquires a green color owing to the presence of traces of chromium it is called emerald. Blue colored beryl is called aquamarine, pink color (less common) is called morganite, yellow is heliodor. Emerald (and other beryl) crystals mostly form within a hydrothermal environment when the elements, aluminum, beryllium and silica are present in the ideal amounts and combine in a chemical reaction to form crystals of beryl. When chromium is present the crystals acquire the rich green color of emerald. Beryl crystals are found within veins and embedded in the host rocks.
Mining methods
The mining methods employed for emeralds is still rather primitive. The tools commonly used are hand chisels, sickles, sticks and hammers to procure the stone from the host rock. Explosives are only used when absolutely necessary due to the very real danger such a practice might have on any fine (and valuable) crystals.
Two main mining methods are employed:
- Shaft mining / tunnel mining: Shafts and / or tunnels are dug in the ground and the gems procured.
- Terrace mining: Emerald bearing veins are exposed by digging horizontal terraces in step-like formation along gullies. The surrounding debris is washed away with water released from a lake like reservoir above the cuttings. The emeralds thus procured are washed and sorted into parcels.
Emerald (continued)
Tanzania And Tanzanite
(via YouTube) I found the video about Tanzania/tanzanite + the miners educational and interesting.
Part 1
http://www.youtube.com/watch?v=geQrt1LDvu8
Part 2
http://www.youtube.com/watch?v=NVb2WlKzfL0
Part 1
http://www.youtube.com/watch?v=geQrt1LDvu8
Part 2
http://www.youtube.com/watch?v=NVb2WlKzfL0
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