Sapphires

|| Star Sapphires, and Star Rubies || Symbol ( 3 2/m) Space Group: R 3 c || nε=1.760–1.763, Birefringence 0.008 || https://en.wikipedia.org/wiki/Sapphire
 * ~ Color || Blue, Yellow, Orange, Green, Brown, Purple and Violet ||
 * **Types**
 * ~ Crystal Habit || Massive and Granular ||
 * ~ Crystal System || Trigonal
 * ~ Cleavage || None ||
 * ~ Fracture || Conchoidal, Splintery ||
 * ~ Mohs Scale Hardness || 9.0 ||
 * ~ Luster || Vitreous ||
 * ~ Streak || White ||
 * ~ Specific Gravity || 3.95–4.03 ||
 * ~ Optical Properties || Abbe Number 72.2 ||
 * ~ Refractive Index || nω=1.768–1.772
 * ~ Pleochrism || Strong ||
 * ~ Melting Point || 2030–2050 °C ||
 * ~ Fusibility || Infusible ||
 * ~ Solubility || Insoluble ||
 * ~ Other Characteristics || Coeficient of Thermal Expansion (5.0–6.6)×10−6/K ||

Soriah Ellison