Synthetic Spinel

Mohs Hardness: 7.5-8
Specific Gravity: 3.58-3.63
Reflective Index: 1.72
Crystal structure: Isometric (cubic) Chemical composition: Magnesium aluminate. Color: Red, blue, green, purple, orange, gray, brown, near colorless. Synthetic Spinel has often been confused with ruby and sapphire, but it provides many fine gems in its own right. Some famous large "rubies," such as the Black Prince's Ruby and the Timur Ruby in the British Crown Jewels are actually spinels. Fine large stones are rare and expensive, but smaller stones are quite abundant.