Q & A

Trace elements alter colours of gems

Q If rubies and sapphires are the same mineral, why are they of different colours?

A Both rubies and sapphires are mostly the same clear mineral: aluminium oxide in a crystalline form called corundum.

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A version of this article appeared in the print edition of The Straits Times on July 05, 2018, with the headline 'Trace elements alter colours of gems'. Subscribe