| Red Gemstones |
|---|
| Gemstone | Crystal System | Density | Hardness | Refractive index | Treatments |
 Alexandrite |
orthorhombic | 3.72 | 8.5 | 1.746-1.755 | none |
 Beryl |
hexagonal | 2.72 | 7.5-8.9 | 1.577-1.583 | heat, radiation, fracture filling, oiling |
 Coral |
trigonal | 2.65 | 3.5-4.0 | 1.486-1.658 | dying |
 Corundum |
trigonal | 4.00 | 9.0 | 1.762-1.770 | none |
 Diamond |
cubic | 3.52 | 10 | 2.417 | radiation, drilling, fracture filling |
trigonal |
2.8-3.0 | 5-51/2 | 1.598-1.602 | none | |
 Garnet |
cubic | 3.40 | 5.5-6.5 | 1.700-1.746 | none |
| cubic | 2.29 | 6.00 | 1.483-1.487 | none | |
 Kunzite |
monoclinic | 3.18 | 6.0-7.0 | 1.660-1.676 | light will fade |
 Morganite |
hexagonal | 2.72 | 7.5-8.0 | 1.577-1.583 | radiation |
| cubic | 3.5-3.6 | 6½ - 7½ | 1.73-1.76 | Fracture filling | |
 Rhodolite |
cubic | 3.84 | 7.0-7.5 | 1.760 | none |
 Ruby |
hexagonal | 4.00 | 9 | 1.762-1.770 | heat, fracture filling |
 Spinel |
cubic | 3.60 | 8 | 1.718 | none |
 Tourmaline |
trigonal | 3.06 | 7.0-7.5 | 1.630-1.662(red) | heat |
