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Ceylonite, named for the island of Ceylon, is a ferroan spinel with Mg:Fe from 3:1 and 1:1, and little or no ferric iron. Pleonaste is named from the Greek for 'abundant,' for its many crystal forms, and is distinguished chemically by low Mg:Fe ratios of approximately 1:3. It is sometimes used as a gemstone. [2]
It is widely used as an inexpensive cut gem in birthstone jewelry for the month of August. Light blue synthetic spinel is a good imitation of aquamarine beryl, and green synthetic spinel is used as an emerald or tourmaline simulant. [29] By 2015, transparent spinel was being made in sheets and other shapes through sintering. [30]
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
Main chrysoberyl producing countries. The mineral or gemstone chrysoberyl is an aluminate of beryllium with the formula Be Al 2 O 4. [5] [6] The name chrysoberyl is derived from the Greek words χρυσός chrysos and βήρυλλος beryllos, meaning "a gold-white spar".
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Taaffeite (/ ˈ t ɑː f aɪ t /; BeMgAl 4 O 8) is a mineral, named after its discoverer Richard Taaffe (1898–1967) who found the first sample, a cut and polished gem, in October 1945 in a jeweler's shop in Dublin, Ireland. [4] [5] As such, it is the only gemstone to have
Samarian Spinel, the world's largest spinel; Menshikov Ruby, the world's second largest spinel set on top of the Great Imperial Crown of Russia; Timur Ruby, believed to be a ruby until 1851, hence its name; Black Prince's Ruby, the famous spinel mounted on the Imperial State Crown of the United Kingdom
Ceylonite (variety of spinel) Chalcedony (cryptocrystalline variety of quartz and moganite) Chiastolite (variety of andalusite) Chlorastrolite (variety of pumpellyite-(Mg)) Chrysoprase (green nickel bearing chalcedony) Chrysotile (group name - asbestiform serpentine) Citrine (yellow variety of quartz) Cleveite (variety of uraninite)