| 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 Sillimanite
Sillimanite is an alumino-silicate mineral with the chemical formula Al2SiO5. Sillimanite is a very rare trimorph and it has a common variety called fibrolite.
Color: violet blue, grey green, colorless, brown, green,
Categories: semi-precious stone
Chemical Composition: Al2OSiO4
Crystal Group: Orthorhombic
Refractive Index: 1.658 - 1.678
Hardness: 6 - 7.5
Density: 3.25
Occurrence: France, Madagascar, U.S.A., Sri Lanka, Burma. Kenya
|  Natural Tourmaline
Tourmaline is actually a group of several different minerals which have similar crystal structures, but complex and variable chemical formulas. Tourmaline is the most varicolored of all gemstones. It occurs in all colors, but red, green, and multicolored are its most famous gem colors.
Color: blue, bluish green, green, greenish blue, green-blue or blue-green, greenish yellow, orangy red, red, red-orange or orange-red, red-purple or purple-red, slightly purplish red, slightly yellowish green, strongly purplish red, strongly yellowish green, very slightly bluish green, yellowish green, yellow-green or green-yellow, colorless, brown, pink
Categories: semi-precious stone
Chemical Composition: (NaCa)(LI,MgFe,Al)9B3Si6(O,OH)31
Crystal Group: Hexagonal
Refractive Index: 1.624(+.005, -.005) - 1.644(+.006, -.006)
Hardness: 7-7.5
Density: 3.06 (.05, +.15)
Occurrence: Brazil, East Africa, Nigeria, Madagascar, U.S.A.
|  Natural Triplite
Triplite is a rare fluoro-hydroxide phosphate mineral that forms in phosphate rich granitic pegmatites and high temperature hydrothermal veins. The name is from the Greek triplos for triple, in reference to the three cleavage directions. It is a very gemstones and few cut stones have been ever reported.
Color: brightly coloured (brown, salmon, flesh-red)
Categories: semi-precious stone
Chemical Composition: (Mn,Fe2+)2(PO4)(F,OH)
Crystal Group: Monoclinic
Refractive Index: 1.650 - 1.680
Hardness: 5 - 5.5
Density: 3.44 - 3.90
Occurrence: the Shigar Valley, Pakistan; China; France, Bavaria, Germany; Kimito, Finland; Karibib, Namibia; Maine, and Connecticut, Arizona and Colorado in the United States.
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