"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