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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Table of Refractive Indices and Double Refraction of Selected Gems
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
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.
International Gem Society
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