A gemstone or gem (also called as precious stone or semi-precious stone, a fine gem, or jewel) is a piece of mineral, which, in cut and polish form, is used to make jewelry or other adornments.
The colours of Gemstones – Precious Stones are affected by differences in chemical and atomic structure, leading to the absorption of the different wavelengths of light. Their hardness is measured on the Mohs scales, which runs from 1-10.
The colour chemistry of following gemstones is described in following infographic. Alexandrite, Amethyst, Aquamarine, Diamond, Emerald, Garnet, Opal, Pearl, Peridot, Ruby, Sapphire, Spinel, Topaz, Tourmaline, Turquoise and Zircon.
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You can read article on the chemical composition of gemstones and download pdf of this infographic on Compound Interest.