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Download as PDF; Printable version; In other projects Wikimedia Commons ... There are a number of organic materials used as gems, including: Amber; Ammolite ...
Many gems are crystals which are classified by their crystal system such as cubic or trigonal or monoclinic. Another term used is habit, the form the gem is usually found in. [12] For example, diamonds, which have a cubic crystal system, are often found as octahedrons. [13] Gemstones are classified into different groups, species, and varieties.
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 ...
The green gem at right is a type of grossular known as tsavorite. Grossular is a calcium-aluminium garnet with the formula Ca 3 Al 2 (SiO 4 ) 3 , though the calcium may in part be replaced by ferrous iron and the aluminium by ferric iron.
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Inclusions are one of the most important factors when it comes to gem valuation. They diminish the clarity and value of many gemstones, such as diamonds, and increase the value of others, such as star sapphires. [5] Many colored gemstones are expected to have inclusions which do not greatly affect their values. They are categorized into three ...
GIA also exists to educate the gem and jewelry industry and the general public through its publications and outreach efforts. Most notable of these efforts is the quarterly publication of the magazine Gems & Gemology, a respected journal in the field. The journal includes full-length feature articles, as well as reports on GIA research ...
Gems & Gemology is a quarterly scientific journal published by the Gemological Institute of America. Each issue is devoted to research on diamonds , gemstones , and pearls . Topics include geographic sources, imitations and synthetics, treatments, and identification techniques.