| Gemstone Chart |
 Natural Iolite
Iolite is a popular and interesting gemstone, and is the gem variety of the mineral cordierite.It has also been called water sapphire because it looks very much like a blue sapphire.
Color: violet, blue, dark blue,
Categories: semi-precious stone
Chemical Composition: MG2AL4SI5O18
Crystal Group: Orthorhombic
Refractive Index: 1.53 - 1.55
Hardness: 7 - 7.5
Density: 2.57 - 2.66
Occurrence: Sri Lanka; Burma; India; Tsivory,Madagascar; Canada; Namibia; Tanzania; Norway; U.S.A.; Brazil
|  Natural Opal
Opal is the most colorful of all gems. It is a form of silica chemically similar to quartz, but more like glass and containing a variable amount of water within the mineral structure. Its splendid play of color is unsurpassed, and fine examples can be more valuable than diamond. Precious opals (black and white) are cut and polished into cabochons and used in all forms of jewelry.
Color: White, green, blue, black, red, orange, violet, pink, grey, yellow.
Categories: precious stone
Chemical Composition: SIO2nH2O
Crystal Group: Amorphous
Refractive Index: 1.44-1.46
Hardness: 5.5 - 6.0
Density: 2.65 - 3.00
Occurrence: Czechoslovakia, Mexico, Honduras, Australia, Brazil, Tanzania.
|  Natural Spinel
Spinel is the magnesium aluminium member of the larger spinel group of minerals. It has the formula MgAl2O4.Pure spinel is white, but impurities give it a wide range of colors.Almost all colors are used in jewelry, but the most valuable and popular color is the deep red. Spinel is cut into gems for use as jewelry. The deep-red variety, known as ruby spinel, is the most prized form.
Color: orange, pink, black, blue, lavender, mauve, greenish blue, and vivid red
Categories: semi-precious stone
Chemical Composition: MgAl2O4
Crystal Group: Cubic
Refractive Index: 1.718 (-.006,+.044)
Hardness: 8
Density: 3.60 (-.03, +.30)
Occurrence: Mogok, Burma; Sri Lanka; Amboseli district, Kenya; Jemaa district, Nigeria; Matombo, Umba, and Tunduru Tanzania; Hunza, Pakistan; Pamir range, Tajikstan; Luc Yen, Vietnam; Madagascar; Australia; Sweden; Brazil.
|  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.
|  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.
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