spinel - gemstone refractive indices and double refraction
spinel - gemstone refractive indices and double refraction

Table of Refractive Indices and Double Refraction of Selected Gems


Refractive indices and double refraction (birefringence) help gemologists identify gems. The following table lists these values for selected gemstones.

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For gemologists, refractive index and double refraction (birefringence) serve as important clues for identifying gems. The following table lists these values for a variety of stones found in jewelry and gem collections.
spinel - gemstone refractive indices and double refraction
Rubies and spinels may show similar colors. One of the simplest ways to distinguish these gems is to test for double refraction with a dichroscope. Since spinels have an isometric crystal structure, they have no double refraction. On the other hand, rubies do have double refraction. Brilliant-cut oval spinel, 6.88 cts, recut by AGTA Spectrum Award-winner Mark Kaufman. Mogok gem tract, Myanmar. © Rob Lavinsky, www.iRocks.com. Used with permission.

Refractive Indices and Double Refraction Values

The following table organizes gemstones from highest to lowest refractive indices.

GemstoneRefractive IndexDouble Refraction
Hematite2.940-3.2200.287
Cinnabar2.905-3.2560.351
Proustite2.881-3.0840.203
Pyrargyrite2.880-3.0800.200
Cuprite2.849none
Rutile2.616-2.9030.287
Brookite2.583-2.7000.117
Anatase2.488-2.5640.046-0.067
Diamond2.417-2.419anomalous
Fabulite2.409none
Stibiotantalite2.370-2.4500.080
Sphalerite2.368-2.371none
Crocoite2.290-2.6600.270
Wulfenite2.280-2.4000.120
Tantalite2.260-2.4300.160
Linobate2.210-2.3000.090
Manganotantalite2.190-2.3400.150
Cubic zirconia (CZ)2.150-2.180none
Mimetite2.120-2.1350.015
Phosgenite2.114-2.1450.028
Senarmontite2.087none
Boleite2.030-2.0500.020
Zincite2.013-2.0290.016
Cassiterite1.997-2.0980.096-0.098
Simpsonite1.994-2.0400.058
Gadolinium gallium garnet (GGG)1.970-2.0200.058
Sulfur1.958-2.2450.291
Bayldonite1.950-1.9900.04
Scheelite1.918-1.9370.010-0.018
Andradite garnet1.880-1.940none
Anglesite1.878-1.8950.017
Uvarovite garnet1.865none
Purpurite1.850-1.9200.007
Sphene (titanite)1.843-2.1100.100-0.192
Yttrium aluminum garnet (YAG)1.833-1.835none
Zircon1.810-2.0240.002-0.059
Cerussite1.804-2.0790.274
Gahnite1.791-1.818none
Spessartite garnet1.790-1.820none
Painite1.787-1.8160.029
Monazite1.774-1.8490.049-0.055
Almandine garnet1.770-1.820none
Gadolinite1.770-1.8200.01-0.04
Ruby (corundum)1.762-1.7780.008
Sapphire (corundum)1.762-1.7780.008
Benitoite1.757-1.8040.047
Shattuckite1.752-1.8150.063
Chrysoberyl1.746-1.7630.007-0.011
Periclase1.740none
Scorodite1.738-1.8160.027-0.030
Staurolite1.736-1.7620.010-0.015
Grossular garnet1.734-1.759none
Chambersite1.732-1.7440.012
Hessonite garnet1.730-1.757none
Epidote1.729-1.7680.015-0.049
Pyroxmangite1.726-1.7640.016-0.020
Azurite1.720-1.8480.108-0.110
Pyrope garnet1.720-1.756none
Hodgkinsonite1.719-1.7480.022-0.026
Taaffeite1.719-1.7300.004-0.009
Rhodonite1.716-1.7520.010-0.014
Gahnospinel1.715-1.754none
Spinel1.712-1.762none
Kyanite1.710-1.7340.015-0.033
Adamite1.708-1.7600.048-0.050
Diaspore1.702-1.7500.048
Serendibite1.701-1.7430.005
Sapphirine1.701-1.7340.004-0.007
Aegirine-augite1.700-1.8000.030-0.050
Idocrase (vesuvianite)1.700-1.7230.002-0.012
Tanzanite1.691-1.7000.009
Neptunite1.690-1.7360.029-0.045
Willemite1.690-1.7230.028-0.033
Rhodizite1.690none
Triphylite1.689-1.7020.006-0.008
Lithiophilite1.680-1.7000.01
Dumortierite1.678-1.6890.015-0.037
Legrandite1.675-1.7400.060
Hypersthene1.673-1.7310.010-0.016
Parisite1.671-1.7720.081-0.101
Clinozoisite1.670-1.7340.010
Sinhalite1.665-1.7120.036-0.042
Lawsonite1.665-1.6860.019-0.021
Diopside1.664-1.7300.024-0.031
Bustamite1.662-1.7070.014-0.015
Kornerupine1.660-1.6990.012-0.017
Hiddenite1.660-1.6810.014-0.016
Kunzite1.660-1.6810.014-0.016
Boracite1.658-1.6730.010-0.011
Axinite1.656-1.7040.010-0.012
Malachite1.655-1.9090.254
Sillimanite1.655-1.6840.014-0.021
Jadeite1.652-1.6880.20
Peridot1.650-1.7030.036-0.038
Ludlamite1.650-1.6970.038-0.044
Enstatite1.650-1.6800.009-0.012
Euclase1.650-1.6770.019-0.025
Phenakite1.650-1.6700.016
Dioptase1.644-1.7090.051-0.053
Jet1.640-1.680none
Eosphorite1.638-1.6710.028-0.035
Spurrite1.637-1.6810.039-0.040
Jeremejevite1.637-1.6530.007-0.013
Barite1.636-1.6480.012
Siderite1.633-1.8750.242
Danburite1.630-1.6360.006-0.008
Clinohumite1.629-1.6740.028-0.041
Apatite1.628-1.6490.002-0.006
Andalusite1.627-1.6490.007-0.013
Friedelite1.625-1.6640.030
Smithsonite1.621-1.8490.228
Datolite1.621-1.6750.040-0.050
Celestite1.619-1.6350.010-0.012
Tourmaline1.614-1.6660.014-0.032
Actinolite1.614-1.6530.020-0.025
Hemimorphite1.614-1.6360.022
Lazulite1.612-1.6460.031-0.036
Prehnite1.611-1.6690.021-0.039
Gaspéite1.610-1.8100.22
Turquoise1.610-1.6500.040
Topaz1.609-1.6430.008-0.016
Sugilite1.607-1.6110.001-0.004
Sogdianite1.606-1.6080.002
Brazilianite1.602-1.6230.019-0.021
Rhodochrosite1.600-1.8200.208-0.220
Odontolite1.600-1.6400.010
Nephrite1.600-1.6270.027
Pectolite (larimar)1.595-1.6450.038
Montebrasite1.594-1.6330.22
Phosphophyllite1.594-1.6210.021-0.033
Meliphanite1.593-1.6120.019
Eudialyte1.591-1.6330.003-0.010
Chondrodite1.592-1.6460.028-0.034
Catapleiite1.590-1.6290.039
Wardite1.590-1.5990.009
Herderite1.587-1.6270.023-0.032
Colemanite1.586-1.6150.028-0.030
Howlite1.586-1.6050.019
Zektzerite1.582-1.5850.003
Amblygonite1.578-1.6460.024-0.030
Ekanite1.572-1.5730.001
Anhydrite1.570-1.6140.044
Augelite1.570-1.5900.014-0.020
Emerald (beryl)1.565-1.6020.006
Aquamarine (beryl)1.564-1.5960.004-0.005
Variscite1.563-1.5940.031
Beryl (precious)1.562-1.6020.004-0.010
Tremolite1.560-1.6430.017-0.027
Vivianite1.560-1.6400.050-0.075
Serpentine1.560-1.5710.008-0.014
Larbradorite1.559-1.5700.008-0.010
Hambergite1.553-1.6280.072
Pyrophyllite1.552-1.6000.048
Muscovite1.552-1.6180.036-0.043
Beryllonite1.552-1.5610.009
Charoite1.550-1.5610.004-0.009
Amethyst (quartz)1.544-1.5530.009
Aventurine (quartz)1.544-1.5530.009
Rose quartz1.544-1.5530.009
Citrine (quartz)1.544-1.5530.009
Prasiolite (quartz)1.544-1.5530.009
Smoky quartz1.544-1.5530.009
Rock crystal (quartz)1.544-1.5530.009
Andesine1.543-1.5510.008
Oligoclase1.542-1.5490.007
Talc1.540-1.5900.050
Scapolite1.540-1.5790.006-0.037
Petrified Wood1.540none
Jasper1.540none
Amber1.539-1.545none
Ivory1.535-1.570none
Apophyllite1.535-1.5370.002
Tiger's eye1.534-1.540none
Aragonite1.530-1.6850.155
Agate1.530-1.5400.004-0.009
Chalcedony1.530-1.5400.004-0.009
Chrysoprase1.530-1.5400.004-0.009
Moss agate1.530-1.5400.004-0.009
Sepiolite1.530none
Witherite1.529-1.6770.148
Milarite1.529-1.5510.003
Nepheline1.526-1.5460.0004
Sunstone1.525-1.5480.01
Cordierite1.522-1.5780.008-0.018
Iolite (cordierite)1.522-1.5780.008-0.018
Amazonite1.522-1.5300.008
Pearl1.520-1.6900.156
Ammolite1.520-1.6800.155
Strontianite1.520-1.6700.150
Gypsum1.520-1.5290.009
Orthoclase1.518-1.5300.008
Sanidine1.518-1.5300.008
Moonstone1.518-1.5260.008
Pollucite1.517-1.525none
Carletonite1.517-1.5210.004
Stichtite1.516-1.5440.026
Thomsonite1.515-1.5420.006-0.025
Magnesite1.509-1.7170.022
Scolecite1.509-1.5250.007-0.012
Leucite1.504-1.5090.001
Mesolite1.504-1.5080.001
Dolomite1.502-1.6980.185
Petalite1.502-1.5190.012-0.017
Lapis lazuli1.500none
Haüyne1.496-1.510none
Tugtupite1.496-1.5020.006
Cancrinite1.495-1.5280.024-0.029
Celluloid1.495-1.520none
Ulexite1.491-1.5200.029
Yugawaralite1.490-1.5090.011-0.014
Whewellite1.489-1.6510.159-0.163
Kurnakovite1.488-1.5250.036
Inderite1.486-1.5070.017-0.020
Calcite1.486-1.6580.172
Coral1.486-1.6580.160-0.172
Moldavite1.48-1.540none
Natrolite1.480-1.4930.013
Sodalite1.480none
Analcime1.479-1.489none
Thaumasite1.464-1.5070.036
Creedite1.461-1.4850.024
Chrysocolla1.460-1.5700.023-0.040
Obsidian1.450-1.550none
Gaylussite1.443-1.5230.080
Glass1.440-1.900none
Fluorite1.434none
Sellaite1.378-1.3900.012
Opal1.370-1.520none
Villiaumite1.327anomalous

Notes

A double refraction of "none" means the stone is either isometric or amorphous. "Anomalous" means this singly refractive stone may show anomalous double refraction (ADR). Singly refractive gems with high refractive indices may show ADR.


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