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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HomeLearning CenterGemologyReference Charts & MaterialsTable of Refractive Indices and Double Refraction of Selected Gems
By International Gem Society, updated on
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.
Refractive Indices and Double Refraction Values
The following table organizes gemstones from highest to lowest refractive indices.
| Gemstone | Refractive Index | Double Refraction |
| Hematite | 2.940-3.220 | 0.287 |
| Cinnabar | 2.905-3.256 | 0.351 |
| Proustite | 2.881-3.084 | 0.203 |
| Pyrargyrite | 2.880-3.080 | 0.200 |
| Cuprite | 2.849 | none |
| Rutile | 2.616-2.903 | 0.287 |
| Brookite | 2.583-2.700 | 0.117 |
| Anatase | 2.488-2.564 | 0.046-0.067 |
| Diamond | 2.417-2.419 | anomalous |
| Fabulite | 2.409 | none |
| Stibiotantalite | 2.370-2.450 | 0.080 |
| Sphalerite | 2.368-2.371 | none |
| Crocoite | 2.290-2.660 | 0.270 |
| Wulfenite | 2.280-2.400 | 0.120 |
| Tantalite | 2.260-2.430 | 0.160 |
| Linobate | 2.210-2.300 | 0.090 |
| Manganotantalite | 2.190-2.340 | 0.150 |
| Cubic zirconia (CZ) | 2.150-2.180 | none |
| Mimetite | 2.120-2.135 | 0.015 |
| Phosgenite | 2.114-2.145 | 0.028 |
| Senarmontite | 2.087 | none |
| Boleite | 2.030-2.050 | 0.020 |
| Zincite | 2.013-2.029 | 0.016 |
| Cassiterite | 1.997-2.098 | 0.096-0.098 |
| Simpsonite | 1.994-2.040 | 0.058 |
| Gadolinium gallium garnet (GGG) | 1.970-2.020 | 0.058 |
| Sulfur | 1.958-2.245 | 0.291 |
| Bayldonite | 1.950-1.990 | 0.04 |
| Scheelite | 1.918-1.937 | 0.010-0.018 |
| Andradite garnet | 1.880-1.940 | none |
| Anglesite | 1.878-1.895 | 0.017 |
| Uvarovite garnet | 1.865 | none |
| Purpurite | 1.850-1.920 | 0.007 |
| Sphene (titanite) | 1.843-2.110 | 0.100-0.192 |
| Yttrium aluminum garnet (YAG) | 1.833-1.835 | none |
| Zircon | 1.810-2.024 | 0.002-0.059 |
| Cerussite | 1.804-2.079 | 0.274 |
| Gahnite | 1.791-1.818 | none |
| Spessartite garnet | 1.790-1.820 | none |
| Painite | 1.787-1.816 | 0.029 |
| Monazite | 1.774-1.849 | 0.049-0.055 |
| Almandine garnet | 1.770-1.820 | none |
| Gadolinite | 1.770-1.820 | 0.01-0.04 |
| Ruby (corundum) | 1.762-1.778 | 0.008 |
| Sapphire (corundum) | 1.762-1.778 | 0.008 |
| Benitoite | 1.757-1.804 | 0.047 |
| Shattuckite | 1.752-1.815 | 0.063 |
| Chrysoberyl | 1.746-1.763 | 0.007-0.011 |
| Periclase | 1.740 | none |
| Scorodite | 1.738-1.816 | 0.027-0.030 |
| Staurolite | 1.736-1.762 | 0.010-0.015 |
| Grossular garnet | 1.734-1.759 | none |
| Chambersite | 1.732-1.744 | 0.012 |
| Hessonite garnet | 1.730-1.757 | none |
| Epidote | 1.729-1.768 | 0.015-0.049 |
| Pyroxmangite | 1.726-1.764 | 0.016-0.020 |
| Azurite | 1.720-1.848 | 0.108-0.110 |
| Pyrope garnet | 1.720-1.756 | none |
| Hodgkinsonite | 1.719-1.748 | 0.022-0.026 |
| Taaffeite | 1.719-1.730 | 0.004-0.009 |
| Rhodonite | 1.716-1.752 | 0.010-0.014 |
| Gahnospinel | 1.715-1.754 | none |
| Spinel | 1.712-1.762 | none |
| Kyanite | 1.710-1.734 | 0.015-0.033 |
| Adamite | 1.708-1.760 | 0.048-0.050 |
| Diaspore | 1.702-1.750 | 0.048 |
| Serendibite | 1.701-1.743 | 0.005 |
| Sapphirine | 1.701-1.734 | 0.004-0.007 |
| Aegirine-augite | 1.700-1.800 | 0.030-0.050 |
| Idocrase (vesuvianite) | 1.700-1.723 | 0.002-0.012 |
| Tanzanite | 1.691-1.700 | 0.009 |
| Neptunite | 1.690-1.736 | 0.029-0.045 |
| Willemite | 1.690-1.723 | 0.028-0.033 |
| Rhodizite | 1.690 | none |
| Triphylite | 1.689-1.702 | 0.006-0.008 |
| Lithiophilite | 1.680-1.700 | 0.01 |
| Dumortierite | 1.678-1.689 | 0.015-0.037 |
| Legrandite | 1.675-1.740 | 0.060 |
| Hypersthene | 1.673-1.731 | 0.010-0.016 |
| Parisite | 1.671-1.772 | 0.081-0.101 |
| Clinozoisite | 1.670-1.734 | 0.010 |
| Sinhalite | 1.665-1.712 | 0.036-0.042 |
| Lawsonite | 1.665-1.686 | 0.019-0.021 |
| Diopside | 1.664-1.730 | 0.024-0.031 |
| Bustamite | 1.662-1.707 | 0.014-0.015 |
| Kornerupine | 1.660-1.699 | 0.012-0.017 |
| Hiddenite | 1.660-1.681 | 0.014-0.016 |
| Kunzite | 1.660-1.681 | 0.014-0.016 |
| Boracite | 1.658-1.673 | 0.010-0.011 |
| Axinite | 1.656-1.704 | 0.010-0.012 |
| Malachite | 1.655-1.909 | 0.254 |
| Sillimanite | 1.655-1.684 | 0.014-0.021 |
| Jadeite | 1.652-1.688 | 0.20 |
| Peridot | 1.650-1.703 | 0.036-0.038 |
| Ludlamite | 1.650-1.697 | 0.038-0.044 |
| Enstatite | 1.650-1.680 | 0.009-0.012 |
| Euclase | 1.650-1.677 | 0.019-0.025 |
| Phenakite | 1.650-1.670 | 0.016 |
| Dioptase | 1.644-1.709 | 0.051-0.053 |
| Jet | 1.640-1.680 | none |
| Eosphorite | 1.638-1.671 | 0.028-0.035 |
| Spurrite | 1.637-1.681 | 0.039-0.040 |
| Jeremejevite | 1.637-1.653 | 0.007-0.013 |
| Barite | 1.636-1.648 | 0.012 |
| Siderite | 1.633-1.875 | 0.242 |
| Danburite | 1.630-1.636 | 0.006-0.008 |
| Clinohumite | 1.629-1.674 | 0.028-0.041 |
| Apatite | 1.628-1.649 | 0.002-0.006 |
| Andalusite | 1.627-1.649 | 0.007-0.013 |
| Friedelite | 1.625-1.664 | 0.030 |
| Smithsonite | 1.621-1.849 | 0.228 |
| Datolite | 1.621-1.675 | 0.040-0.050 |
| Celestite | 1.619-1.635 | 0.010-0.012 |
| Tourmaline | 1.614-1.666 | 0.014-0.032 |
| Actinolite | 1.614-1.653 | 0.020-0.025 |
| Hemimorphite | 1.614-1.636 | 0.022 |
| Lazulite | 1.612-1.646 | 0.031-0.036 |
| Prehnite | 1.611-1.669 | 0.021-0.039 |
| Gaspéite | 1.610-1.810 | 0.22 |
| Turquoise | 1.610-1.650 | 0.040 |
| Topaz | 1.609-1.643 | 0.008-0.016 |
| Sugilite | 1.607-1.611 | 0.001-0.004 |
| Sogdianite | 1.606-1.608 | 0.002 |
| Brazilianite | 1.602-1.623 | 0.019-0.021 |
| Rhodochrosite | 1.600-1.820 | 0.208-0.220 |
| Odontolite | 1.600-1.640 | 0.010 |
| Nephrite | 1.600-1.627 | 0.027 |
| Pectolite (larimar) | 1.595-1.645 | 0.038 |
| Montebrasite | 1.594-1.633 | 0.22 |
| Phosphophyllite | 1.594-1.621 | 0.021-0.033 |
| Meliphanite | 1.593-1.612 | 0.019 |
| Eudialyte | 1.591-1.633 | 0.003-0.010 |
| Chondrodite | 1.592-1.646 | 0.028-0.034 |
| Catapleiite | 1.590-1.629 | 0.039 |
| Wardite | 1.590-1.599 | 0.009 |
| Herderite | 1.587-1.627 | 0.023-0.032 |
| Colemanite | 1.586-1.615 | 0.028-0.030 |
| Howlite | 1.586-1.605 | 0.019 |
| Zektzerite | 1.582-1.585 | 0.003 |
| Amblygonite | 1.578-1.646 | 0.024-0.030 |
| Ekanite | 1.572-1.573 | 0.001 |
| Anhydrite | 1.570-1.614 | 0.044 |
| Augelite | 1.570-1.590 | 0.014-0.020 |
| Emerald (beryl) | 1.565-1.602 | 0.006 |
| Aquamarine (beryl) | 1.564-1.596 | 0.004-0.005 |
| Variscite | 1.563-1.594 | 0.031 |
| Beryl (precious) | 1.562-1.602 | 0.004-0.010 |
| Tremolite | 1.560-1.643 | 0.017-0.027 |
| Vivianite | 1.560-1.640 | 0.050-0.075 |
| Serpentine | 1.560-1.571 | 0.008-0.014 |
| Larbradorite | 1.559-1.570 | 0.008-0.010 |
| Hambergite | 1.553-1.628 | 0.072 |
| Pyrophyllite | 1.552-1.600 | 0.048 |
| Muscovite | 1.552-1.618 | 0.036-0.043 |
| Beryllonite | 1.552-1.561 | 0.009 |
| Charoite | 1.550-1.561 | 0.004-0.009 |
| Amethyst (quartz) | 1.544-1.553 | 0.009 |
| Aventurine (quartz) | 1.544-1.553 | 0.009 |
| Rose quartz | 1.544-1.553 | 0.009 |
| Citrine (quartz) | 1.544-1.553 | 0.009 |
| Prasiolite (quartz) | 1.544-1.553 | 0.009 |
| Smoky quartz | 1.544-1.553 | 0.009 |
| Rock crystal (quartz) | 1.544-1.553 | 0.009 |
| Andesine | 1.543-1.551 | 0.008 |
| Oligoclase | 1.542-1.549 | 0.007 |
| Talc | 1.540-1.590 | 0.050 |
| Scapolite | 1.540-1.579 | 0.006-0.037 |
| Petrified Wood | 1.540 | none |
| Jasper | 1.540 | none |
| Amber | 1.539-1.545 | none |
| Ivory | 1.535-1.570 | none |
| Apophyllite | 1.535-1.537 | 0.002 |
| Tiger's eye | 1.534-1.540 | none |
| Aragonite | 1.530-1.685 | 0.155 |
| Agate | 1.530-1.540 | 0.004-0.009 |
| Chalcedony | 1.530-1.540 | 0.004-0.009 |
| Chrysoprase | 1.530-1.540 | 0.004-0.009 |
| Moss agate | 1.530-1.540 | 0.004-0.009 |
| Sepiolite | 1.530 | none |
| Witherite | 1.529-1.677 | 0.148 |
| Milarite | 1.529-1.551 | 0.003 |
| Nepheline | 1.526-1.546 | 0.0004 |
| Sunstone | 1.525-1.548 | 0.01 |
| Cordierite | 1.522-1.578 | 0.008-0.018 |
| Iolite (cordierite) | 1.522-1.578 | 0.008-0.018 |
| Amazonite | 1.522-1.530 | 0.008 |
| Pearl | 1.520-1.690 | 0.156 |
| Ammolite | 1.520-1.680 | 0.155 |
| Strontianite | 1.520-1.670 | 0.150 |
| Gypsum | 1.520-1.529 | 0.009 |
| Orthoclase | 1.518-1.530 | 0.008 |
| Sanidine | 1.518-1.530 | 0.008 |
| Moonstone | 1.518-1.526 | 0.008 |
| Pollucite | 1.517-1.525 | none |
| Carletonite | 1.517-1.521 | 0.004 |
| Stichtite | 1.516-1.544 | 0.026 |
| Thomsonite | 1.515-1.542 | 0.006-0.025 |
| Magnesite | 1.509-1.717 | 0.022 |
| Scolecite | 1.509-1.525 | 0.007-0.012 |
| Leucite | 1.504-1.509 | 0.001 |
| Mesolite | 1.504-1.508 | 0.001 |
| Dolomite | 1.502-1.698 | 0.185 |
| Petalite | 1.502-1.519 | 0.012-0.017 |
| Lapis lazuli | 1.500 | none |
| Haüyne | 1.496-1.510 | none |
| Tugtupite | 1.496-1.502 | 0.006 |
| Cancrinite | 1.495-1.528 | 0.024-0.029 |
| Celluloid | 1.495-1.520 | none |
| Ulexite | 1.491-1.520 | 0.029 |
| Yugawaralite | 1.490-1.509 | 0.011-0.014 |
| Whewellite | 1.489-1.651 | 0.159-0.163 |
| Kurnakovite | 1.488-1.525 | 0.036 |
| Inderite | 1.486-1.507 | 0.017-0.020 |
| Calcite | 1.486-1.658 | 0.172 |
| Coral | 1.486-1.658 | 0.160-0.172 |
| Moldavite | 1.48-1.540 | none |
| Natrolite | 1.480-1.493 | 0.013 |
| Sodalite | 1.480 | none |
| Analcime | 1.479-1.489 | none |
| Thaumasite | 1.464-1.507 | 0.036 |
| Creedite | 1.461-1.485 | 0.024 |
| Chrysocolla | 1.460-1.570 | 0.023-0.040 |
| Obsidian | 1.450-1.550 | none |
| Gaylussite | 1.443-1.523 | 0.080 |
| Glass | 1.440-1.900 | none |
| Fluorite | 1.434 | none |
| Sellaite | 1.378-1.390 | 0.012 |
| Opal | 1.370-1.520 | none |
| Villiaumite | 1.327 | anomalous |
Notes
If a gemstone listing has "none" for double refraction, it means the stone is either isometric or amorphous. "Anomalous" indicates that a singly refractive gem may exhibit anomalous double refraction (ADR). Gems with high refractive indices are more likely to display this optical effect.
International Gem Society
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