Gemology Hub | Gemstone & Mineral Identification Guides

Gemological Properties of Corundum S.No Description Physical properties / Optical properties 1 Chemical formula Al 2 O 3 2 Group Corundum 3 Crystal system Trigonal / Hexagonal 4 Color Colorless , Red, blue, green, orange, pink, yellow 5 Specific gravity 3.95 to 4 6 Hardness 9 7 Durability Excellent 8 R.I 1.762 to 1.770 9 Fluoresce Varies 10 Optical sign Uniaxial Negative 11 Inclusions Mostly, liquid inclusions, Needles, solid inclusions

  Gemological Properties of Fluorite S.No Description Fluorite Physical properties / Optical properties 1 Chemical formula CaF 2 2 Crystal system Cubic 3 Color Multi color , blue, green, colorless etc 4 Specific gravity 3.18 to 3.31 5 Hardness 4 6 Durability Poor 7 R.I 1.43 8 Fluoresce Inert to strong blue

  Afganite Properties S.No Description   Physical properties / Optical properties 1 Chemical formula (Na,Ca,K)8(Si,Al)12O24(SO4,Cl,CO3)3•(H2O) 2 Group Cancrinite 3 Crystal system Hexagonal 4 Color Mostly Blue 5 Specific gravity 2.56 to 2.85 6 Hardness 5.5 to 6 7 Durability Fair 8 R.I 1.522 to 1.533 9 Fluoresce Bright orange in long waves / inert in short waves 10 Optical sign Uniaxial negative 11 Inclusions May be speckled of dark blue inclusions of Lazurite

 Weight Estimation Tables for Colored Gems   To obtain approximate weights of the following shapes of colored stones multiply by the following measurements to millimeters. A listing of the specific gravities is below.   Round Faceted = ...................Diameter x diameter x depth x SG x .0018 Oval Faceted = .......................Diameter x diameter x depth x SG x .0020 Emerald Faceted = .................Length x width x depth x SG x .0025 Rectangle Faceted = .............Length x width x depth x SG x .0026 Square Faceted = ...................Length x width x depth x SG x .0025 Marquise Faceted = ...............Length x width x depth x SG x .0017 Pear Faceted = ........................Length x width x depth x SG x .0018 Heart Faceted = ...