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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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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