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Spinel

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description Spinel Overview

Spinel is a magnesium aluminum oxide mineral that crystallizes in the cubic system, highly valued as a gemstone for its hardness and vibrant array of colors. Due to its similar appearance and formation environments, red spinel has been historically confused with ruby for centuries. This confusion is most famously exemplified by the 170-carat Black Prince's Ruby, a large red spinel currently set in the British Imperial State Crown. Modern gemologists now easily distinguish the stones using differences in their crystal structures and refractive properties, establishing spinel as a distinct jewel.

help Spinel FAQ

Why was red spinel historically mistaken for ruby?

Red spinel and ruby can occur together in the same deposits and look extremely similar without modern gemological testing. Ruby is corundum, while spinel is a magnesium aluminium oxide with a different crystal structure.

Is the Black Prince's Ruby really a ruby?

No, it is a large red spinel set in the British Imperial State Crown. The approximately 170-carat stone was called a ruby for centuries before mineralogical distinctions became reliable.

How can a gemologist distinguish spinel from ruby?

Spinel is singly refractive, whereas ruby is doubly refractive, and the two minerals also differ in hardness and optical properties. Laboratory testing can additionally identify characteristic inclusions and spectral patterns.

Does natural spinel come in colors besides red?

Yes, natural spinel occurs in pink, blue, violet, orange, gray, and black as well as red. Cobalt can produce especially vivid blue material, while chromium contributes to desirable reds and pinks.

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