oxides
Spinel
MgAl2O4
- Also known as
- balas rubyceylonite
- Crystal system
- cubic
- Hardness
- 8 on the Mohs scale
- Lustre
- vitreous
- Colour
- Red, pink, blue, violet, black
- Where it forms
- In marbles and in aluminium-rich metamorphic rocks, very often in the same deposits as ruby, which is precisely why the two were confused for so long.
- Chiefly from
- Mogok, MyanmarLuc Yen, VietnamTanzaniaSri Lanka
Why it is that colour
Chromium for red, iron and zinc for blue, and cobalt for the rare and intense blue that collectors chase.
Safety
No hazard from handling. Spinel is one of the very few gems that is almost never treated, which is part of its appeal to collectors.
Where it comes from
Burmese and Vietnamese material dominates the fine end. Tanzanian and Sri Lankan production is significant. Small volumes overall.
Historical use
The Black Prince’s Ruby and the Timur Ruby, both in the British royal collection, are spinels, as are several of the most famous stones in the Iranian crown jewels. In 1783 Jean-Baptiste Louis Rome de l’Isle established that spinel and ruby were different minerals, and a large part of European royal gemmology had to be rewritten.
Recorded as history and attributed where possible. That a stone was used for something establishes that people used it, not that it worked.
What is attributed to it, and since when
Its entire historical reputation was borrowed, because until the 1780s it was simply called ruby. The great "balas rubies" of medieval Europe — the name derives from Badakhshan — were spinels from Afghanistan, and everything attributed to them was attributed under a different stone’s name.
Described, not endorsed. Dating a claim is not the same as assessing it — but an association that first appears in a book published in 1985 is not an ancient inheritance, whatever the label says. A sincere account of feeling better is compatible with the stone doing nothing — see the placebo effect.
Sold as this, but not
Worth knowing
Spinel is the connoisseur's argument against reputation. It is hard, brilliant, comes in extraordinary colours, is almost never treated, and is rarer in fine quality than ruby — and for two centuries after it was distinguished from ruby it was regarded as a lesser stone precisely because it was not one.
Its status has risen sharply since about 2005, mostly on the strength of cobalt-blue material from Vietnam and Tanzania. Nothing changed about the mineral. What changed was that dealers began telling its story instead of apologising for it.
Identity checked against IMA-CNMNC master list, June 2025.