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CORUNDUM COLOR CHART What is Corundum and What are its Basic Qualities? A: Corundum is an aluminum oxide that commonly forms hexagonal barrel-shaped prisms that taper at both ends or as thin tabular hexagonal plates. It has a hardness of 9 on the Mohs scale, making it one of the most durable commercial gemstones. It has no dominant cleavage and fractures in a conchoidal manner. A high density of ~4.0 g/cm3 (most silicate minerals are ~2.6 g/cm3) results in corundum occurring in secondary placer deposits and recoverable by panning methods, similar to how you would recover placer gold. Corundum comesin all colours of the rainbow but is most commonly found as opaque crystals with dull colours.Red corundumis called ruby, blue corundum is called sapphire, and all other colours are called fancy sapphires. Some varieties of corundum will fluoresce under short wave and long wave UV light if there is enough chromium in the crystal structure but little iron, which tends to quench any emitted energy. Physical Properties of Corundum: Mohs Hardness: 9 Specific Gravity: 3.90 to 4.05 Cleavage Quality:None Fracture: Uneven,Conchoidal Optical Properties of Corundum: Refractive Index: 1.758 to 1.780 Optical Character: Uniaxial/- Birefringence 0.007 to 0.010 Pleochroism Dichroism: blue - violet-blue and greenish-blue; green - yellowish-green; yellow - pale yellow; purple - violet; orange, yellowish-red - deep crimson. Dispersion:0.018 Corundum and Spinel colors-6mm Round stones: Corundum and Spinel colors Sample Box for sale:6mm Round stones : $25/pc Slide Show of the Corundum Color chart 6mm round stones:   Or you can Click this picture to view the Clear pictures of Corundum Color chart 6mm round stones in Google album:   3mm Round Faceted Corundum Gemstones All colors (Google Album) Link:https://photos.app.goo.gl/TzBLy3Zs81U4unoJ7 The Popular Colors of Corundum: Pink Sapphire: 1#, 2#, #3 Ruby Red: #5, #7 and #8 Blue Sapphire: #33...