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.
3 Minute Read
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
Related Articles
Specific Gravity Values of Selected Gems
Measuring specific gravity helps gemologists identify gemstones. The following table lists the specific gravity values for a variety of gem...
Read More
List of False or Misleading Gemstone Names
A list of False or Misleading Gemstone Names and its Actual Gemological Name. Gathered by the source "Gemstones of the...
Read More
Weights and Measures Conversion Chart
Printable chart to convert weights and measures including Carats, Grams, Kilograms, Ounces, Pounds and Troy Ounces Pounds and Pennyweights.
Read More
Diamond Lookalikes Listed by Specific Gravity
Distinguishing diamond lookalikes from the real thing can be challenging. Learn how to use specific gravity and birefringence to make...
Read More
Latest Articles
800 Years of Mogok: A Celebration in Tenuous Times
As Mogok, Myanmar prepares to celebrate its 800th anniversary, the inhabitants of this prolific gem producing region face an uncertain...
Read More
What is the Average Gemstone Faceting Yield?
What’s the average gemstone faceting yield from a single piece of rough? Learn how to estimate how much material you’ll...
Read More
Pyroxmangite Value, Price, and Jewelry Information
Pyroxmangite grains are rare, seldom clean enough to facet, and difficult to cut. However, when cut, they are extremely beautiful...
Read More
How to Identify Emerald Simulants and Synthetics
Gemologists can separate natural emeralds from emerald simulants and synthetics. Learn about the most common tools and techniques for this....
Read More
Never Stop Learning
When you join the IGS community, you get trusted diamond & gemstone information when you need it.
Get Gemology Insights
Get started with the International Gem Society’s free guide to gemstone identification. Join our weekly newsletter & get a free copy of the Gem ID Checklist!