Gemstones with RI 1.800
7 gemstones have a refractive index range that includes 1.800. 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 |
|---|---|---|---|---|
| Almandine Garnet | 1.770 – 1.830 | 3.93 – 4.30 | Cubic | SR |
| Star Garnet | 1.770 – 1.830 | 3.93 – 4.30 | Cubic | SR |
| Spessartite Garnet | 1.790 – 1.815 | 4.12 – 4.18 | Cubic | SR |
| Low-Type Zircon | 1.780 – 1.815 | 3.90 – 4.10 | Tetragonal | SR |
| Malachite | 1.655 – 1.909 | 3.60 – 4.05 | Monoclinic | DR_B- |
| Benitoite | 1.757 – 1.804 | 3.64 – 3.68 | Hexagonal | DR_U+ |
| Rhodochrosite | 1.600 – 1.820 | 3.40 – 3.70 | Trigonal | DR_U- |