What exactly gives precious and semiprecious stones their “identity”?

Question

I’m used to classifying stones by their color (i.e. purple=amethyst). How is it possible to have pink sapphires or blue topaz? Is it the internal structure of the stone?

In: Other

Answer 1

Impurities and/or metals in the structure of the stone. The crystalline structure of the stone results in a clear object, but there are other elements trapped within the structure that cause light to come out at different wavelengths.