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Currently, almost all prasiolite on the market is made from amethyst via a process of heating and irradiation. [5] Green quartz is sometimes incorrectly called green amethyst, [6] which is not an acceptable name for the material according to Federal Trade Commission Guidelines. Other names for green quartz include vermarine and lime citrine. [7]
Clarity grading in coloured gemstones is based on the eye-clean standard, that is, a gem is considered flawless if no inclusions are visible with the unaided eye (assuming 20/20 vision). [29] The Gemological Institute of America classifies tanzanite as a Type I gemstone, meaning it is normally eye-clean.
Topaz is a silicate mineral made of aluminum and fluorine with the chemical formula Al 2 Si O 4 (F, OH) 2.It is used as a gemstone in jewelry and other adornments. Common topaz in its natural state is colorless, though trace element impurities can make it pale blue or golden brown to yellow-orange. [7]
A ring is a round band, usually made of metal, worn as ornamental jewelry. The term "ring" by itself denotes jewellery worn on the finger; when worn as an ornament elsewhere, the body part is specified within the term, e.g., earrings, neck rings , arm rings , and toe rings .
Most citrine is made by heating amethyst, and partial heating with a strong gradient results in "ametrine" – a stone partly amethyst and partly citrine. Aquamarine is often heated to remove yellow tones, or to change green colors into the more desirable blue, or enhance its existing blue color to a deeper blue.
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