| Gemstone Chart |
 Natural Peridot
Peridot is the best known gem variety of olivine, a species name for a series of magnesium-iron rich silicate minerals.It is one of the prettiest of all green gems.Most peridot formed deep inside the earth and was brought to the surface by volcanoes. Some has also come to Earth in meteorites, but this extraterrestrial peridot is extremely rare, and you're not likely to see it in a retail jewelry store.
Color: Green, olive.
Categories: semi-precious stone
Chemical Composition: (Mg,Fe)2(SiO)4
Crystal Group: Orthorhombic
Refractive Index: 1.654-1.689
Hardness: 6.5
Density: 3.34
Occurrence: China, Burma, East Africa, U.S.A., and Vietnam
|  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 Sapphirine
Sapphirine is a rare mineral, a silicate of magnesium and aluminium.Though Sapphirine clearly falls into the "rare stone" category, it is a relatively durable stone with a Moh's hardness of 7.5. Sapphirine's very distinctive appearance along with their somewhat unusual durability have made them fairly popular with collectors.
Color: Pale blue, bluish gray, greenish gray, green, purplish pink
Categories: semi-precious stone
Crystal Group: Monoclinic
Refractive Index: 1.714-1.723
Hardness: 7.5
Density: 3.4-3.5
Occurrence: U.S.A., U.K., Sweden, Czechoslovakia, Japan, South Africa, Greenland, Madagascar, Italy, Sri Lanka
|  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 Sphene
Sphene is also known as calcium titanium silicate.It is named from the greek word for wedge, because of its typical wedge shaped crystal habit.Because of it's high dispersion and refractive index, a well cut sphene can display stunning brilliance. Sphene is somewhat soft and as a result is more suitable as a pendant than as a ring stone. Sphene is rarely very clean.
Color: Green, yellow. brown
Categories: semi-precious stone
Chemical Composition: CaTiSiO5
Crystal Group: Monoclinic
Refractive Index: (1.885-1.990,)-(1.915-2.050)
Hardness: 5.5
Density: 3.52-3.54
Occurrence: Austria, Dheirene-Madagascar, India, USA, Brazil.
|  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 Turquoise
Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium.The gem turquoise owes it's beauty almost entirely to its superb color. It has been used for ornamentation since 3000BC and possibly before.
Color: Blue, Greenish Blue
Categories: semi-precious stone
Chemical Composition: CuAl6(PO4)4(OH)85H2O
Crystal Group: Triclinic
Refractive Index: 1.62
Hardness: 5.5-6
Density: 2.60- 2.90
Occurrence: Iran, USA, India, Tibet, China, Egypt, Chile, Russia, Australia
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