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C.S.I.*
*(Colored Stone Identification)

The instruments do not lie! So often, a gem can be misidentified because we make assumptions based on our first impressions when looking at a stone. ("It's red. It must be a ruby or a garnet").Using our instruments first, can avoid some embarrassing mistakes.

Below is a table of refractive indices, LOW to HIGH. More selections will be added as time permits. I'm going to start with stones we will most commonly encounter.

> > ±
Refractive Indices
Birefringence
Specific Gravity
Optic Chartacter
Identity
1.434 ±

-

3.18±0.01
isotropic
Fluorite
1.44  
2.05±
isotropic
Imitation Opal

1.44 to 1.90

-
2.3-4.5
isotropic
Glass
1.450 +0.020
  -0.08
-
2.15
+0.07
 
-0.90
isotropic
Opal/ Fire Opal
1.45 to 1.55
-
2.45
+0.05
 
-0.10
isotropic
Obsidian
1.483 ± 0.003
-
2.20-2.40
isotropic
Sodalite
1.486-1.658
0.172
2.65 ± 0.05
1-
Coral
1.486-1.658
0.172
2.70±0.01
1-
Calcite
1.500
-
2.75 ± 0.25
isotropic
Lapis Lazuli
1.50: approx
-
2.38
isotropic
Lapis: Gilson imitation
1.50
-
2.40 ± 0.04
isotropic
Moldavite
1.518-1.526±0.004
0.008
2.56 ± 0.01
2-
Orthoclase: Moonstone or Sanidine
1.522-1.530
0.008
2.56 ± 0.01
2-
Amazonite
1.53-1.69
0.16
2.66 +0.12
  -0.05
-
Pearls
1.53-1.69
0.16
2.72+0.06
-
Cultured Pearls

1.532( ±0.007)-
1.542( ±0.006)

0.010
2.65±0.02
1-
Aventurine Feldspar (pladgioclase w/ flecks of hematite)
1.535-1.539±0.005
0.004-0.006
2.60±0.05
1+
Chacedony
1.54 (1.539-1.545)
-
1.08±0.02
isotropic
Amber
1.54 (1.535-1.57)
-
1.85±0.15
isotropic
Ivory
1.542-1.551 +0.045
  -0.011
0.008-0.009
2.61±0.05
2-

Cordierite /Iolite

1.544-1.553±
0.009
2.66±0.01
1+
Quartz
 1.559-1.568 ± 0.002
0.009-0.011
2.70±00.05
2+
Labradorite:Plagioclase
1.560-1.563 +0.004
  -0.003
0.003-0.004
2.65±
1-
Synthetic Emerald: Lechleitner IV
 1.561-1.564±
0.003-0.005
2.65±0.01
1-
Synthetic Emerald: Chatham
 1.562-1.567±0.012
0.005-0.008
2.68
1-
Synthetic Emerald: Gilson
 1.566-1.570
0.004-0.006
2.68
1-
Synthetic Emerald: Lechleitner II
 1.566-1.571+0.007
0.005-0.006
2.68±0.01
1-
Synthetic Emerald: Linde
 1.569-1.574±
0.005
2.70
1-
Synthetic Emerald: Lechleitner III
 1.570-1.575±0.004
0.005-0.009
2.70±0.02
1-
Heliodor
 1.570±0.005-
1.575 ±0.006
0.005-0.009
2.69±0.02
1-
Emerald: Brazil
 1.570-1.576±0.006
0.005-0.009
2.70±0.02
1-
Emerald: Colombia
 1.575±0.011-
1.580 ±0..016
0.005-0.009
2.71±0.03
1-
Aquamarine
 1.575-1.581 ±
0.006
2.69
1-
Synthetic Emerald: Lechleitner I
1.577

+0.016
-0.015-

1.583 +0.019
-0.015
0.006
2.72 +0.15
  -0.04
1-
Beryl
 1.579-1.585±0.002
0.005-0.009
2.73±0.02
1-
Emerald: Urals
1.580- +0.020
-0.002
1.790 +0.030
-0.004
0.210
(0.208-0.220)
3.68 +0.02
  -0.23
1-
Aggregate
Rhodochrosite
 1.581-1.590±0.001
0.009
2.71-2.76
1-
Emerald: Zambia
 1.585-1.592±0.003
0.005-0.009
2.74±0.02
1-
Emerald: Africa/India
 1.585-1.594±0.006
0.005-0.009
2.82±0.05
1-
Morganite
 1.602-1.621±0.003
0.019-0,021
2.94±0.03
2+
Brazilianite
 1.606-1.632±0.006
0.026-0.027
2.95±0.08
2-
Nephrite
 1.610-1.650
0.040
2.76+0.08
       -0.45
2+
Turquoise
 1.612-1.636
0.020-0.027
3.02±0.04
   
2±
Amblygonite
 1.616-1.641
0.022-0.027
3.00+0.10
       -0.05
2-
A ggregate
Actinolite
1.619- +0.014
-0.010
1.627 +0.016
-0.010
0.008
3.53±0.04
2+
Topaz
 1.616-1.640±0.002
0.024
3.05-3.06
1-
Tourmaline: Brown
 1.630-1.636±0.003
0.006
3.00±0.03
2+
Danburite
 1.616-1.640±0.002
0.024
3.05-3.06
1-
Tourmaline: Brown
 1.634-1.638±0.012
0.002-0.008
3.18±0.05
1-
Apatite
1.624- +0.015
0.010
1.644 +0.022
-0.010
0.020
3.06+0.15
        -0.05
1-
Tourmaline
 1.627-1.640
0.013
3.17
2-
Andalusite
1.642- +0.005
-0.014
1.648 +0.003
-0.014
0.002-0.006
3.17
1-
Apatite
 1.654-1.690±0.013
0.036-0.038
3.14±0.14
2+
Peridot
 1.660-1.676±0.005
0.014-0.016
3.18±0.03
2+
Spodumene
 1.660-1.680±0.008
0.020
3.34±0.04
2+
aggregate
Jadeite
 1.660-1.910
0.250
3.95±0.15
2-
Malachite
 1.675-1.701
0.024-0.030
3.29±0.11
2-
Diopside
 1.678-1.688
0.010-0.012
3.29±0.07
2-
Axinite
 1.690-1.700
0.010
3.35-3.55
2+
Zoisite: Tanzanite
 1.700 to1.712
-
3.32-3.36
isotropic
Garnet: Grossular
 1.712-1.725
-
3.60±0.06
isotropic
Spinel
 1.716-1.744
-
3.40-3.74
2+
Rhodonite
 1.730
-
3.65±0.13
isotropic
Synthetic Spinel
 1.734±0.025
-
3.61±0.12
isotropic
Green Transparent Grossular
 1.740±0.017
-
3.61±0.12
isotropic
Hessonite
 1.746±0.026
-
3.78±0.16
isotropic
Pyrope
 1.746-1.755±0.005
0.007-0.011
3.73±0.02
2+
Chrysoberyl: Alexandrite
 1.760±0.020
-
3.84±0.10
isotropic
Rhodolite
 1.762-1.770±0.010
0.008
3.99±0.04
1-
Sapphire
  1.762-1.770±0.008
0.008
4.00±0.03
1-
Ruby
 1.790±0.030
-
4.05±0.12
isotropic
Almandine