eli5 What determines whether a gem is a sapphire, ruby, emerald, diamond, etc if those gems don’t necessarily have to be the most common thought color? For example, sapphires can be colors other than blue. What’s the difference between a red sapphire and a ruby?

Question

eli5 What determines whether a gem is a sapphire, ruby, emerald, diamond, etc if those gems don’t necessarily have to be the most common thought color? For example, sapphires can be colors other than blue. What’s the difference between a red sapphire and a ruby?

In: 5800

Answer 1

Gemstones are usually different minerals (although some organic materials are worn as gems in jewelry like pearls and amber) and most of them get their color from structural or chemical impurities that refract light in different parts of the spectrum.

Interestingly enough there’s a pretty large variety of quartz that would include rose quartz, amethyst, citrine, ametrine, jasper, and agate but aside from color I’m not entirely sure what would make those quartz varieties distinct.

Fun fact though: peridots are always green.