Red Spinel, the Ruby That Was Not

Spinel is magnesium aluminium oxide, and red spinel is coloured, like ruby, by chromium; because it occurs alongside ruby in the same marble-hosted deposits of Burma and central Asia and shows a very similar red, it was for centuries not distinguished from ruby at all. Several of the most famous rubies in the world are in fact spinels: the Black Prince's Ruby and the Timur Ruby in the British Crown Jewels are both red spinels.

The distinction was only established as mineralogy matured, and the recognition somewhat unfairly demoted the stone in the market despite its beauty and its hardness of 8. Spinel is singly refractive and often remarkably clean. It has little independent folklore, its history being folded into that of ruby; modern birthstone lists have added spinel as an alternate for August. Its metaphysical associations are recent and largely inherited from ruby by association.