| Blue Gemstones |
|---|
| Gemstone | Crystal System | Density | Hardness | Refractive index | Treatments |
 Agate |
microcrystalline | 2.66 | 6.5-7.0 | 1.544-1.553 | dying |
 Aquamarine |
hexagonal | 2.72 | 7.5-8.0 | 1.577-1.583 | heat |
| hexagonal | 3.2 | 5 | 1.63-1.64 | heat | |
 Azurite |
monoclinic | 3.7-3.8 | 3.5-4.0 | 1.730-1.838 | none |
 Benitoite |
hexagonal | 3.64 | 6.0-6.5 | 1.757-1.804 | none |
 Chrysocolla |
microcrystalline | 2.00-2.24 | 2-4 | 1.54 | none |
 Corundum |
trigonal | 4.00 | 9.0 | 1.762-1.770 | heat |
 Diamond |
cubic | 3.52 | 10 | 2.417 | radiation, drilling, fracture filling |
| Lapis
Lazuli |
various | 2.75 | 5.50 | 1.500 | none |
 Moonstone |
monoclinic | 2.56 | 6.0-6.5 | 1.518-1.526 | none |
| Sapphire |
hexagonal | 4.00 | 9 | 1.762-1.770 | heat, fracture filling |
 Spinel |
cubic | 3.60 | 8 | 1.718 | none |
 Tanzanite |
orthorhombic | 3.30 | 6.0-7.0 | 1.690-1.700 | heat |
 Topaz |
orthorhombic | 3.53 | 8.0 | 1.619-1.627 | blue is irradiated |
 Tourmaline |
trigonal | 3.06 | 7.0-7.5 | 1.624-1.644 | heat |
 Turquoise |
triclinic | 2.73 | 5.0-6.0 | 1.610-1.650 | dying, sealing |
 Zircon |
tetragonal | 4.00 | 6.50 | 1.810-1.815 | none |
