Corundum gemological properties

Gemological Properties of Corundum

S.No	Description	Physical properties / Optical properties
1	Chemical formula	Al2O3
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

Fluorite and its properties

 

Gemological Properties of Fluorite

S.No	Description	Fluorite Physical properties / Optical properties
1	Chemical formula	CaF2
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

Gemological properties of Afganite

 

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

Colored Gems Weight Estimation Tables

 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 = ......................Length x width x depth x SG x .0018