Gemstones with RI 1.550
17 gemstones have a refractive index range that includes 1.550. 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 |
|---|---|---|---|---|
| Amethyst | 1.544 – 1.553 | 2.63 – 2.65 | Trigonal | DR_U+ |
| Ametrine | 1.544 – 1.553 | 2.63 – 2.67 | Trigonal | DR_U+ |
| Aventurine | 1.544 – 1.553 | 2.64 – 2.69 | Trigonal | AGG |
| Citrine | 1.544 – 1.553 | 2.63 – 2.65 | Trigonal | DR_U+ |
| Hawk's Eye | 1.544 – 1.553 | 2.64 – 2.71 | Trigonal | AGG |
| Prasiolite | 1.544 – 1.553 | 2.63 – 2.67 | Trigonal | DR_U+ |
| Rock Crystal | 1.544 – 1.553 | 2.63 – 2.65 | Trigonal | DR_U+ |
| Rose Quartz | 1.544 – 1.553 | 2.63 – 2.65 | Trigonal | DR_U+ |
| Smoky Quartz | 1.544 – 1.553 | 2.63 – 2.65 | Trigonal | DR_U+ |
| Tiger's Eye | 1.544 – 1.553 | 2.64 – 2.71 | Trigonal | AGG |
| Charoite | 1.550 – 1.559 | 2.54 – 2.68 | Monoclinic | AGG |
| Sunstone | 1.537 – 1.572 | 2.62 – 2.65 | Triclinic | DR_B- |
| Chrysocolla | 1.460 – 1.630 | 2.00 – 2.40 | Amorphous | AGG |
| Scapolite | 1.540 – 1.572 | 2.50 – 2.74 | Tetragonal | DR_U- |
| Coral | 1.486 – 1.658 | 2.60 – 2.70 | Aggregate | AGG |
| Lapis Lazuli | 1.500 – 1.670 | 2.70 – 2.90 | Aggregate | AGG |
| Pearl | 1.520 – 1.690 | 2.60 – 2.85 | Aggregate | AGG |