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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 ...
A mixture of other minerals, often including pyrite. Lapis lazuli (UK: / ˌlæpɪs ˈlæz (j) ʊli, ˈlæʒʊ -, - ˌli /; US: / ˈlæz (j) əli, ˈlæʒə -, - ˌli /), or lapis for short, is a deep-blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color.
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
Turquoise. Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium, with the chemical formula Cu Al 6(PO 4)4(OH)8·4 H 2 O. It is rare and valuable in finer grades and has been prized as a gemstone for millennia due to its hue.
Logan Sapphire. Star of Bombay, given to Mary Pickford by Douglas Fairbanks, Sr. Star of India. Stuart Sapphire. Black Star of Queensland. Star of Adam, with a weight of 1,404.49 carats (280.898 g), it is the largest star sapphire in the world. Queen Marie of Romania Sapphire.
Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide (α-Al 2 O 3) with trace amounts of elements such as iron, titanium, cobalt, lead, chromium, vanadium, magnesium, boron, and silicon.
The first rank of gemstones, or precious stones, includes ruby, sapphire, diamond, and emerald. Orange topaz, also known as precious topaz, is the birthstone for the month of November, the symbol of friendship, and the state gemstone of the U.S. state of Utah. [24] Blue topaz is the state gemstone of the US state of Texas. [25]
Opal is a hydrated amorphous form of silica (SiO 2 · n H 2 O); its water content may range from 3% to 21% by weight, but is usually between 6% and 10%. Due to its amorphous property, it is classified as a mineraloid, unlike crystalline forms of silica, which are considered minerals. It is deposited at a relatively low temperature and may occur ...