Gemstones with RI 1.665
17 gemstones have a refractive index range that includes 1.665. 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 |
|---|---|---|---|---|
| Hiddenite | 1.660 – 1.676 | 3.15 – 3.21 | Monoclinic | DR_B+ |
| Kunzite | 1.660 – 1.676 | 3.15 – 3.21 | Monoclinic | DR_B+ |
| Enstatite | 1.663 – 1.673 | 3.20 – 3.30 | Orthorhombic | DR_B+ |
| Phenakite | 1.654 – 1.670 | 2.95 – 2.97 | Trigonal | DR_U+ |
| Jet | 1.640 – 1.680 | 1.10 – 1.40 | Amorphous | SR |
| Jadeite | 1.654 – 1.688 | 3.24 – 3.43 | Aggregate | AGG |
| Peridot | 1.654 – 1.690 | 3.27 – 3.48 | Orthorhombic | DR_B+ |
| Kornerupine | 1.660 – 1.699 | 3.27 – 3.45 | Orthorhombic | DR_B- |
| Clinohumite | 1.625 – 1.675 | 3.13 – 3.35 | Monoclinic | DR_B+ |
| Sinhalite | 1.665 – 1.712 | 3.47 – 3.50 | Orthorhombic | DR_B- |
| Prehnite | 1.611 – 1.665 | 2.82 – 2.94 | 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- |
| Rhodochrosite | 1.600 – 1.820 | 3.40 – 3.70 | Trigonal | DR_U- |
| Pearl | 1.520 – 1.690 | 2.60 – 2.85 | Aggregate | AGG |
| Lapis Lazuli | 1.500 – 1.670 | 2.70 – 2.90 | Aggregate | AGG |
| Malachite | 1.655 – 1.909 | 3.60 – 4.05 | Monoclinic | DR_B- |