Although often confused with ruby, spinel stands on its own merits. Available in an outstanding array of colours, its long history includes many famous large spinels still in existence in Europe’s crown jewels. In ancient times, Southeast Asia’s mines yielded exceptional large spinel crystals, which became the treasured property of kings and emperors. Spinel, like garnet and diamond, is singly refractive, with the same physical properties in all crystal directions. Well-formed spinel crystals are fairly common in nature. Spinel was recently added as an August birthstone, sharing this month with peridot and sardonyx.