Sapphire
Sapphire is one of the top four in popularity of gems; Diamond, Sapphire, Ruby, and Emerald. This is mostly due to its beauty, variety of colors and toughness as a jewelry gem. It is typically thought of as being a blue gem, but it is available in many other colors including blue-green, green, violet, purple, orange, yellow, golden, peachy pink, pink, colorless, and black. Ruby is the red or the pinkish red variety of Corundum. With a Moh’s hardness of 9.0 and no cleavage, it is a very durable gem for jewelry.
Sapphire is available from many locations around the world. Some of these locations, like Cambodia, Ceylon, and Kashmir, are well known for their fine Sapphires.
| Category: | Oxide mineral |
| Formula: | Al2O3 |
| Aluminium oxide | |
| Crystallography: | Trigonal – Hexagonal Scalenohedral |
| Crystal Habit: | Crystals hexagonal, prismatic or steeply dipyramidal, tabular, rhombohedral, rarely acicular, typically rough, to 1 m; sectorially striated on [0001] k [1011]. Also granular, massive. |
| Twinning: | Common lamellar k [1011], may be an exsolution phenomenon. Contact or penetration twins on [0001] or [1011], rare. |
| Cleavage: | None; Partings on [0001] and [1011] |
| Fracture: | Irregular/Uneven, Conchoidal |
| Tenacity: | Brittle |
| Hardness (Mohs): | 9.0 |
| Density: | 3.99 – 4.10 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Colorless, Gray, Brown, Pink, Orange, Yellow, Green, Blue to Cornflower Blue, Violet; may be color zoned, asteriated |
| Transparency: | Transparent to Translucent, Opaque |
| Luster: | Adamantine to Vitreous, Pearly on partings |
| Refractive Index: | 1.760 – 1.772 Uniaxial ( – ); commonly anomalously Biaxial |
| Birefringence: | 0.008 – 0.009 |
| Dispersion: | 0.018 (low) |
| Pleochroism: | Weak; e = blue-green to yellow-green, o = pale to deep blue |
| Other: | Asterism often present due to oriented needle-like inclusions or to colloidal or other material deposited in oriented tubules. |
