Gemstones with RI 1.690
9 gemstones have a refractive index range that includes 1.690. 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 |
|---|---|---|---|---|
| Sinhalite | 1.665 – 1.712 | 3.47 – 3.50 | Orthorhombic | DR_B- |
| Star Diopside | 1.664 – 1.721 | 3.27 – 3.36 | Monoclinic | DR_B- |
| Chrome Diopside | 1.664 – 1.730 | 3.22 – 3.38 | Monoclinic | DR_B- |
| Kornerupine | 1.660 – 1.699 | 3.27 – 3.45 | Orthorhombic | DR_B- |
| Peridot | 1.654 – 1.690 | 3.27 – 3.48 | Orthorhombic | DR_B+ |
| Rhodochrosite | 1.600 – 1.820 | 3.40 – 3.70 | Trigonal | DR_U- |
| Diaspore | 1.685 – 1.752 | 3.30 – 3.39 | Orthorhombic | DR_B+ |
| Pearl | 1.520 – 1.690 | 2.60 – 2.85 | Aggregate | AGG |
| Malachite | 1.655 – 1.909 | 3.60 – 4.05 | Monoclinic | DR_B- |