| Gemstone Chart |
 Natural Prehnite
Prehnite is a hydrated calcium aluminum silicate that occurs in a soft yellow-green to apple-green color.It was a rare gemstone, most prehnite is translucent but transparent specimens are sometimes found.While you are unlikely to find it in your local jewelry store, gemstone dealers often have some supply. Deposits are found in South Africa, Australia, China, Scotland and the United States.
Color: yellow green, brown, yellow brown, oil green
Categories: semi-precious stone
Chemical Composition: (CA2Al2SI3O10(OH)2)
Crystal Group: Orthorhombic
Refractive Index: 1.61 - 1.64
Hardness: 6
Density: 2.80 - 2.95
Occurrence: China, France, U.S.A., Scotland, Australia
|  Natural Topaz
Topaz is a silicate mineral most often found in igneous rocks of felsic composition. It is a common gemstone that has been used for centuries in jewelry. Gem quality topaz most commonly occurs in nature as a colorless crystal. It is a very popular gemstone.
Color: colorless, blue, yellow-brown, pinkish orange, red-orange, red-brown, tan.
Categories: semi-precious stone
Chemical Composition: AL(F,OH)2SIO4
Crystal Group: Orthorhombic
Refractive Index: 1.629 - 1.637
Hardness: 8
Density: 3.52 - 3.56
Occurrence: Brazil, Sri Lanka, Nigeria, Germany, Australia, Japan, Russia, Ireland, Zimbabwe.
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