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Zoisite occurs as prismatic, orthorhombic (2/m 2/m 2/m) crystals or in massive form, being found in metamorphic and pegmatitic rock. Zoisite may be blue to violet, green, brown, pink, yellow, gray, or colorless. Blue crystals are known under the name tanzanite. It has a vitreous luster and a conchoidal to uneven fracture. When euhedral, zoisite ...
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 hide
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 ...
Tanzanite forms as a brownish crystal and is trichroic, which means it shows three colours – brown, blue and violet – concurrently. Heating, either underground naturally by metamorphic processes, or artificially, removes the brown or burgundy colour component to produce a stronger violet-blue color and makes the stone "dichroic", which ...
TanzaniteOne traditionally sell only rough gemstones to wholesale customers called "Sightholders", [2] adopting a sales strategy which is based on the Debeers style of distribution where the sightholder companies are guaranteed a consistent bulk supply of the gemstone, but must purchase all quality grades of the gem as opposed to selecting the ...
The collection contains works published from 1496 to the present, encompassing the history and modern development of gemology. Subjects include natural and synthetic gemstones, gem treatments, jewelry design, manufacturing, and marketing. The Liddicoat Library is open to the public and the jewelry trade for on-campus research.
Peridot (gem-quality olivine) Perlite (volcanic glass) Phengite (variety of muscovite) Phosphorite (name given to impure, massive apatite.) Pimelite; Pitchblende (a massive impure form of uraninite) Plessite (mixture of kamacite and taenite) Potassium alum or potash alum (as a mineral, is called alum-(K))
Asterism on the surface of a blue star sapphire. A purple-pink star sapphire displaying asterism in a platinum ring.. An asterism (from Ancient Greek ἀστήρ (astḗr) 'star' and -ism) is a star-shaped concentration of light reflected or refracted from a gemstone.