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en.wikipedia.org/wiki/Gemstone

A gemstone is a piece of mineral crystal which, in cut and polished form, is used to make ... For example, diamonds are made of carbon (C) and rubies of aluminium oxide (Al 2O 3). Next, many gems are crystals which are classified by their ...

www.gemrock.net/learn/gemstones

What Makes A Mineral A Gemstone? ... To qualify as a gem, the specimen should be hard and tough to resist scratching and have beautiful clarity, colour or 'fire'.

www.gemsociety.org/article/how-gems-are-classified

For example, all minerals that contain silica are ... Identifying the class of the gem makes it ...

www.gemsociety.org/article/gem-formation

An explanation of how gems are formed, and how and why gem quality crystals ... Tanzanite is a prime example, as are some unique varieties of garnet. ... ( Remember that a mineral is defined by a combination of its chemical make up and its ...

www.minerals.net/resource/Mineral_Value.aspx

For example, the mineral Rhodochrosite usually has a high value because its ... of undesirable coatings will also make a mineral more aesthetic and desirable.

geologycafe.com/gems/chapter2.html

The structure of minerals and their bonding make a lot of the difference in the minerals' properties, for example hardness. These factors, particularly the ...

geologycafe.com/gems/chapter1.html

This chapter is an introduction to gems in relation to rocks and minerals. ... relatively universal cultural mystique make them the icon of "precious gemstones. .... Halite (salt) has the same cubic crystal shape no matter if the sample is fist- sized or ...

geology.com/minerals/topaz.shtml

This cleavage makes topaz a more fragile gemstone than its hardness of 8 would ... They have the value of a mineral specimen and the value of a gem material.

geology.com/minerals/rhodochrosite.shtml

A pink manganese carbonate mineral used as an ore, a gemstone, and a crystal ... The slabs can then be used to make cabochons, small boxes, or other ...

www.gemselect.com/other-info/minerals-rocks-gems.php

Dec 21, 2007 ... What is the difference between a mineral, a rock and a gemstone? ... of a gemstone is not particularly scientific since it does not make much ...