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GIA Colored Stones Final Notes
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GIA Colored Stones Final Notes
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GIA Colored Stones Final Notes1980 most quantity produced Ruby - ANS-Thailand and Cambodia. They heated them
to 800-1250 in oxidizing environment to remove blue color. Also worked for Myanmar
and Vietnam.
Adularescence - ANS-Adularescence comes from adularia, old name for moonstone.
Adularia comes from a city in Switzerland where it was first mined in Mt. Adular.
Afghan Grading System. - ANS-: Nili, highest quality with best indigo color. Asmani, light
blue lapis, color of denim. Sabzi, greenish lapis
Afghan Lapis - ANS-Intense, uniform, md, slvB, contains little or no pyrite and no calcite
Africa Fancy Sapph - ANS-secondary deposits that erode from host rocks. Most
productive is Tanzania. Madagascar has best pink sapphire. Low temperature heating
removes purple
Akoya Pearls - ANS-Produced in Japan, China and Vietnam in the Pinctada Fucata
oyster or the Pinctada chemnitzii, or hybrids. 2-11mm 6-8mm average. Produce lot of
round pearls. rose overtone and excellent luster. Mollusks are generally smaller, 3-5
inches. Akoya are good for matching strands. All akoya mollusks are bred in hatchery.
They prefer cooler water, below 13 degrees the metabolism slows. Phytoplankton have
killed many mollusks, called red tides. Used to be 1000 farms now 500. Japan also
imports shit ton of pearls. 1996 big red tide, they imported mollusks from China. SOme
went to China. Chinese average quality lower than Japanese but top quality same.
Chinese mollusk called P fucata martensii, same as most japanese farmers. Some
researchers identify as P chemnitzii. 2007-2008 typhoon and low demand and people
switching to shrimp.
Alexandrite CC - ANS-Vivid green daylight, red in incandescent.
Alexandrite Synthetics - ANS-Alexandrite synthesizes by Czochralski, floating zone and
flux. 1987, Kyocera, produced synthetic cats eye CC alexandrite.
Almandine and Pyrope - ANS-Almandine contains iron, pyrope contains magnesium.
AMazonite - ANS-Brazil, India, Madagascar, Norway, Russia and the Us
,Amber - ANS-compound of carbon, hydrogen and oxygen, with traces of sulfur. Has to
be atleast a million years old to be called amber. Otherwise its called copal. Red most
valuable. Baltic sea region of europe is biggest producer.
Amber treatments - ANS-aged color is stained amber. You can heat amber in rapeseed
or canola oil. this creates sun spangles. A two stage heating process under pressure in
an autoclave produces green amber. Manufacturers can create large pieeces of amber
by pressing small gem quality pieces or chips together under gentle heat or pressure.
Sometimes this is called ambroid or pressed amber
Ametrine Source - ANS-Bolivia
Ammonite - ANS-fossilized remains of hard shelled squid like marine mollusks that lived
65-395 million years agoossils are usually made up of aragonite, calcite, pyrite, silica.
Major sources are Canda, england, Morocco, Us. Canada
Andalusite color causing - ANS-Andalusite colors caused by Fe and Ti Transfer.
Apatite - ANS-Gem is compound of calcium, phosphorous and chlorine. Madagascar,
brazil, mexico, myanmar are major sources.
Aquamarine - ANS-Traces of iron. Imitators are treated blue topaz, pale blue glass, syn
spinel. Alluvial shows most material. Pakistan important source. China Brazil also.
Clean and pale.
Aquamarine treatment - ANS-Heat treatment. Removes yellow. 250 to 700.
Arizona Amethyst - ANS-20th century, arizona, 4 peaks mine, new discovery heat
treated to lighten dark toned amethyst. Yellow inclusions in amethyst can let us know if it
is heated, yellow means non heated
Australia Opals - ANS-Rich deposits of black, white crystal and boulder opal in Great
Artesian Basin. GAB is the earths largest artesian basin .NSW town of lightning Ridge is
best black opal. 1910. 1920-50 limited. 1958 introduction of mechanical mining which
rebooted supply. Black opal occurs as nodules or seams in sandtones layers 6-18
meters below. White or milky opal was discovered before black. White cliffs in NW NSW,
was AUS first commercial opal field 1884.SA has lots of opal deposits, mainly Coober
pedy.
, Australia Sapph Info - ANS-Commercial quality. Three areas in the east coast. New
South Wales, town of Inverell and Glen Innes; Queensland's Rubyvale and Anakie; sites
within volcanic lava plains. Some think Australia has the most commercial Sapphire. It is
dark, inky blue, with strong greenish tint. Sapphires were found during gold rush in 1850
and tin mining in 1870. New South wales in 1851. Queensland 1875. Commercial
mining in Inverell, NSW began in 1919 and peaked in 1960. Recovered mainly from
secondary deposits, and remains from pyroclastic flows- explosions of hot volcanic
gasses and rocks- and wet volcanic debris. Mechanized mining has government
regulations. Usually 3ct in size. Virtually all heat treated. Cut shallow.
Azurite - ANS-Copper also causes azurite's color, but it is dk B to vB. Usually STL to O.
Azurite share's malachite's softness and poor toughness. Major sources are US,
Namibia, and France.
Basalt heat for ruby - ANS-drops brown hue and removes blue zoning
BC Canada Neprhite - ANS-More than 50 deposits in BC, in a rock belt 1000 miles.
Mount Ogden and Kutcho. Polar jade, BC, is best green nephrite.
Benitoite - ANS-comes from diablo mountain of San Benito county. state gem in 1985. It
is a silicate of barium and titanium. Similar to sphere. It is like sapphire. No commercial
treatments.
best moonstone - ANS-Sri Lanka is a major source of best moonstone. Lower quality is
from Myanmar and India.
Best Nephrite - ANS-Hetian China best nephrite, mutton fat jade, white nephrite.
Best Nephrite luster - ANS-Greasy is best nephrite transparency and luster.
Best peridot source - ANS-Best peridot from myanmar and himalayas of pakistan and
US.
Best spessartine color - ANS-aurora red. slrO. color due to manganese and iron.
Best star ruby - ANS-Rosser Reeves star ruby, is the best.
Biggest tourmaline producer - ANS-Minas Gerais
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