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 | ||||||||
|
- |
|
isotropic |
Opal/ Fire Opal | ||||||||
1.45 to 1.55 | - |
|
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 |
|
- |
Pearls | ||||||||
1.53-1.69 | 0.16 |
2.72+0.06 |
- |
Cultured Pearls | ||||||||
1.532( ±0.007)- |
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 | ||||||||
|
0.008-0.009 |
2.61±0.05 |
2- |
|||||||||
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 | ||||||||
|
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 | ||||||||
|
0.006 |
|
1- |
Beryl | ||||||||
1.579-1.585±0.002 | 0.005-0.009 |
2.73±0.02 |
1- |
Emerald: Urals | ||||||||
|
0.210 (0.208-0.220) |
|
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 | ||||||||
|
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 | ||||||||
|
0.020 |
3.06+0.15 -0.05 |
1- |
Tourmaline | ||||||||
1.627-1.640 | 0.013 |
3.17 |
2- |
Andalusite | ||||||||
|
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 |