Gemstones with RI 1.770
17 gemstones have a refractive index range that includes 1.770. Refractive index measures how much light bends when entering a gem — it's one of the most diagnostic properties for identification. Measured with a gemological refractometer.
| Gemstone | RI Range | SG Range | Crystal System | Optic Character |
|---|---|---|---|---|
| Color-Change Sapphire | 1.762 – 1.770 | 3.99 – 4.01 | Trigonal | DR_U- |
| Padparadscha Sapphire | 1.762 – 1.770 | 3.95 – 4.03 | Trigonal | DR_U- |
| Pink Sapphire | 1.762 – 1.770 | 3.98 – 4.01 | Trigonal | DR_U- |
| Ruby | 1.762 – 1.770 | 3.97 – 4.05 | Trigonal | DR_U- |
| Sapphire | 1.762 – 1.770 | 3.95 – 4.03 | Trigonal | DR_U- |
| Star Ruby | 1.762 – 1.770 | 3.97 – 4.05 | Trigonal | DR_U- |
| Star Sapphire | 1.762 – 1.770 | 3.95 – 4.03 | Trigonal | DR_U- |
| Synthetic Color-Change Corundum | 1.762 – 1.770 | 3.97 – 4.05 | Trigonal | DR_U- |
| White Sapphire | 1.762 – 1.770 | 3.99 – 4.01 | Trigonal | DR_U- |
| Yellow Sapphire | 1.762 – 1.770 | 3.99 – 4.01 | Trigonal | DR_U- |
| Benitoite | 1.757 – 1.804 | 3.64 – 3.68 | Hexagonal | DR_U+ |
| Malachite | 1.655 – 1.909 | 3.60 – 4.05 | Monoclinic | DR_B- |
| Malaya / Umbalite Garnet | 1.730 – 1.780 | 3.65 – 3.87 | Cubic | SR |
| Rhodolite Garnet | 1.740 – 1.770 | 3.74 – 3.94 | Cubic | SR |
| Almandine Garnet | 1.770 – 1.830 | 3.93 – 4.30 | Cubic | SR |
| Star Garnet | 1.770 – 1.830 | 3.93 – 4.30 | Cubic | SR |
| Rhodochrosite | 1.600 – 1.820 | 3.40 – 3.70 | Trigonal | DR_U- |