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)
Friday, November 02, 2007
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
The Economic Way Of Thinking
Good Books: The book The Economic Way Of Thinking, by Paul Heyne + Peter J. Boettke + David L. Prychitko provides a set of economic principles and concepts--then applies these tools of analysis to a wide variety of familiar situations. Example (s) + Application (s) = Good teaching. A must-read book.
Here is what the description of book says (via Amazon):
The Economic Way of Thinking develops the basic principles of micro-and macroeconomic analysis, and rigorously employs them as tools rather than ends unto themselves. This book introduces readers to a method of reasoning; to think like an economist—teaching through example and application. It even teaches by showing learners how not to think, by exposing them to the errors implicit in much popular reasoning about economic events. Chapter topics include opportunity cost and the supply of goods, supply and demand, profit and loss, competition and monopoly, price searching, competition and government policy, the distribution of income, markets and government, the overall performance of economic systems, the supply of money, monetary and fiscal policies, national policies and international exchange, employment and unemployment, promoting economic growth, and the limitations of economics. For individuals seeking a deeper understanding of the effects of world events on the economy and vice versa.
Here is what the description of book says (via Amazon):
The Economic Way of Thinking develops the basic principles of micro-and macroeconomic analysis, and rigorously employs them as tools rather than ends unto themselves. This book introduces readers to a method of reasoning; to think like an economist—teaching through example and application. It even teaches by showing learners how not to think, by exposing them to the errors implicit in much popular reasoning about economic events. Chapter topics include opportunity cost and the supply of goods, supply and demand, profit and loss, competition and monopoly, price searching, competition and government policy, the distribution of income, markets and government, the overall performance of economic systems, the supply of money, monetary and fiscal policies, national policies and international exchange, employment and unemployment, promoting economic growth, and the limitations of economics. For individuals seeking a deeper understanding of the effects of world events on the economy and vice versa.
Thursday, November 01, 2007
The Art No One Sees
(via The Guardian) Robert Tait writes about Tehran's museum of contemporary art + cultural isolationist beliefs of the present regime + general clampdown on social, intellectual and cultural freedoms + other viewpoints @ http://arts.guardian.co.uk/art/news/story/0,,2201065,00.html
The New Visionaries
Barbara Pollack writes about contemporary artists vs. self-taught artists + the do-it-yourself style (s) + the outsider art concept (s) + other viewpoints @ http://artnews.com/issues/article.asp?art_id=1436
Reliance Jewelry India
It has been reported that Reliance Retail, part of Reliance Industries, the crown jewel of corporate India, will be launching Reliance Jewelry, with branding options + sourcing agreement with Rosy Blue, one of the largest jewelry manufacturers, for operations. It's part of the company's lifestyle retail concept, which includes books and music, cosmetics, lifestyle accessories and home solutions. According to consultants Technopak Advisors the Indian jewelry market + the branded jewelry is estimated to grow by 15 per cent + 30 percent annually.
Useful links:
www.ril.com
www.rosyblue.com
Useful links:
www.ril.com
www.rosyblue.com
Roman Jewelers And Lapidaries
(via Roman Book On Precious Stones: 1950) Sydney H Ball writes:
As to the cutting of gems, Pliny states that cut stones with a smooth level surface are preferred to those which exhibit depressions or other irregularities. An oblong shape is best; next to it, the lenticular; after this, circular stones are admired, those which are irregularly angular being held in the least esteem. In explanation, flat stones were preferred to those capable of being cut only cabochon, as the former were suitable for engraving. The oblong had evidently supplanted the ancient lenticular form while the angular was perhaps only used when to cut the rough gem in one of the more desired forms would drastically reduce the weight of a stone. The only stone Pliny mentions as faceted was the beryl (and its variety emerald) and this only by polishing the six faces of the natural prism; a method believed to be the best to increase the stone’s brilliancy. The Hindus, in Pliny’s stime, preferred long hexagonal beryl beads and these, pierced, were strung on elephant’s hair, it being the only stone they wore without gold setting. The piercing evidently improved the color adn transparency of some beryls although the finest were not pierced but were held in place by studs of gold attached to the ends. Beads of plasma and garnet also cut into prisms are from time to time found in Roman ruins, so abundantly indeed that graded necklaces can be made from them. These presumably postdate Pliny’s time. The sardonyx was also pierced and worn in neck ornaments by the poorer people of India. In Pliny’s time, the presence of a hole pierced in the stone proved it of Indian origin, an indication still in instances used by precious stone dealers. The lapidaries of the day hollowed out the lower side of garnets of deep color to give them a lighter and more pleasing hue. While shaped into cups, garnet ‘offers the most obstinate resistance to the graver’. Other stones were most easily cut, that of the callaina (turquoise) being ‘easily done’. Topazos (peridot) is the ‘only stone of high value that yields to the action of the file, the rest being polished by the aid of the stone of Naxos’ (emery). Peridot ‘wears with use’, its softness being the reason why we today rarely set it in rings. Unusually perfect rock crystals called acontetta (without flaw) were set uncut in jewelry.
Pliny states that the skilled artisan can hide the imperfections of rock crystal by cutting and engraving the stone. Tavernier, sixteen hundred years later, warned merchants to examine, with particular care, Indian diamonds with many facets, for the Hindu diamond cutter hid flaws with facets.
The garnets found on the hill of Orthosia in Asia Minor were cut ‘to perfection by the Alabandians’ in the nearby city of Alabanda. The early existence of this cutting center, exclusively for colored stones, is interesting.
Softer stones were shaped by a file but emery was used to cut and polish most gems. The emerald and the sapphire were rarely engraved and, as to the latter, the lapidary usually only polished the surface of the original pebble.
Pliny lists as famous engravers Pyrgoteles, Apollonides, Cronius, and Dioscurides, all Greeks. Alexander the Great permitted Pyrgoteles alone to engrave his likeness. Dioscurides cut a signet with an excellent likeness of Emperor Augustus, a seal thereafter used officially by the Roman Emperors. Gem engraving reached its height under Augustus adn continued on a high plane until the time of Hadrian when it began to deteriorate. Indeed, in general, the decline of classical art appears to have been more or less continuous from about 400 B.C to 200 A.D.
Seneca is the first Roman to speak of cameos (to be specific, a ring set with the head of Tiberius in relief), intaglios having preceded them by thousands of years. A few cameos, however, were cut in Greece and in Etruria early in the 5th century B.C but cameos only became relatively common a couple of centuries later when Indian layered stones were available to the Greek lapidaries. The Babylonians, centuries before, had rather crudely cut a few poor cameos. In Rome cameos which could only be used ornamentally, were never as popular as intaglios which were not only beautiful but also had their practical use as signets.
As to the cutting of gems, Pliny states that cut stones with a smooth level surface are preferred to those which exhibit depressions or other irregularities. An oblong shape is best; next to it, the lenticular; after this, circular stones are admired, those which are irregularly angular being held in the least esteem. In explanation, flat stones were preferred to those capable of being cut only cabochon, as the former were suitable for engraving. The oblong had evidently supplanted the ancient lenticular form while the angular was perhaps only used when to cut the rough gem in one of the more desired forms would drastically reduce the weight of a stone. The only stone Pliny mentions as faceted was the beryl (and its variety emerald) and this only by polishing the six faces of the natural prism; a method believed to be the best to increase the stone’s brilliancy. The Hindus, in Pliny’s stime, preferred long hexagonal beryl beads and these, pierced, were strung on elephant’s hair, it being the only stone they wore without gold setting. The piercing evidently improved the color adn transparency of some beryls although the finest were not pierced but were held in place by studs of gold attached to the ends. Beads of plasma and garnet also cut into prisms are from time to time found in Roman ruins, so abundantly indeed that graded necklaces can be made from them. These presumably postdate Pliny’s time. The sardonyx was also pierced and worn in neck ornaments by the poorer people of India. In Pliny’s time, the presence of a hole pierced in the stone proved it of Indian origin, an indication still in instances used by precious stone dealers. The lapidaries of the day hollowed out the lower side of garnets of deep color to give them a lighter and more pleasing hue. While shaped into cups, garnet ‘offers the most obstinate resistance to the graver’. Other stones were most easily cut, that of the callaina (turquoise) being ‘easily done’. Topazos (peridot) is the ‘only stone of high value that yields to the action of the file, the rest being polished by the aid of the stone of Naxos’ (emery). Peridot ‘wears with use’, its softness being the reason why we today rarely set it in rings. Unusually perfect rock crystals called acontetta (without flaw) were set uncut in jewelry.
Pliny states that the skilled artisan can hide the imperfections of rock crystal by cutting and engraving the stone. Tavernier, sixteen hundred years later, warned merchants to examine, with particular care, Indian diamonds with many facets, for the Hindu diamond cutter hid flaws with facets.
The garnets found on the hill of Orthosia in Asia Minor were cut ‘to perfection by the Alabandians’ in the nearby city of Alabanda. The early existence of this cutting center, exclusively for colored stones, is interesting.
Softer stones were shaped by a file but emery was used to cut and polish most gems. The emerald and the sapphire were rarely engraved and, as to the latter, the lapidary usually only polished the surface of the original pebble.
Pliny lists as famous engravers Pyrgoteles, Apollonides, Cronius, and Dioscurides, all Greeks. Alexander the Great permitted Pyrgoteles alone to engrave his likeness. Dioscurides cut a signet with an excellent likeness of Emperor Augustus, a seal thereafter used officially by the Roman Emperors. Gem engraving reached its height under Augustus adn continued on a high plane until the time of Hadrian when it began to deteriorate. Indeed, in general, the decline of classical art appears to have been more or less continuous from about 400 B.C to 200 A.D.
Seneca is the first Roman to speak of cameos (to be specific, a ring set with the head of Tiberius in relief), intaglios having preceded them by thousands of years. A few cameos, however, were cut in Greece and in Etruria early in the 5th century B.C but cameos only became relatively common a couple of centuries later when Indian layered stones were available to the Greek lapidaries. The Babylonians, centuries before, had rather crudely cut a few poor cameos. In Rome cameos which could only be used ornamentally, were never as popular as intaglios which were not only beautiful but also had their practical use as signets.
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