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Gemstones of the World revised 5th edition, 2013 by Walter Schumann ISBN 978-1454909538 Smithsonian Handbook: Gemstones by Cally Hall, 2nd ed. 2002 ISBN 978-0789489852 v
In 1986, California named benitoite as its state gemstone, a form of the mineral barium titanium silicate that is unique to the Golden State and only found in gem quality in San Benito County. [ 80 ] ^ Colorado is the only state whose geological symbols reflect the national flag's colors: red (rhodochrosite), white (yule marble), and blue ...
Sapphire is one of the two gem-varieties of corundum, the other being ruby (defined as corundum in a shade of red). Although blue is the best-known sapphire color, it occurs in other colors, including gray and black, and also can be colorless. A pinkish orange variety of sapphire is called padparadscha .
The name Almandine is a corruption of Alabanda, a region in Asia Minor where these stones were cut in ancient times. Chemically, almandine is an iron-aluminium garnet with the formula Fe 3 Al 2 (SiO 4) 3; the deep red transparent stones are often called precious garnet and are used as gemstones (being the most common of the gem garnets). [17]
Emerald is a gemstone and a variety of the mineral beryl (Be 3 Al 2 (SiO 3) 6) colored green by trace amounts of chromium or sometimes vanadium. [ 2] Beryl has a hardness of 7.5–8 on the Mohs scale. [ 2] Most emeralds have many inclusions, [ 3] so their toughness (resistance to breakage) is classified as generally poor.
Amethyst. Amethyst is a violet variety of quartz. The name comes from the Koine Greek αμέθυστος amethystos from α- a-, "not" and μεθύσκω ( Ancient Greek) methysko / μεθώ metho ( Modern Greek ), "intoxicate", a reference to the belief that the stone protected its owner from drunkenness. [ 1]
The Gemological Institute of America ( GIA) is a nonprofit institute based in Carlsbad, California. It is dedicated to research and education in the field of gemology and the jewelry arts. [ 1] Founded in 1931, GIA's mission is to protect buyers and sellers of gemstones by setting and maintaining the standards used to evaluate gemstone quality.
Gemstone. Group of precious and semiprecious stones—both uncut and faceted—including ( clockwise from top left) diamond, uncut synthetic sapphire, ruby, uncut emerald, and amethyst crystal cluster. A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or ...