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

To add; long (centuries) before atomic theory and the modern understanding of chemistry relating to minerals, or the tools such as mass spectroscopy that can view the chemical makeup of as substance directly, people could tell these stones apart independent of their visual appearance. They tested for hardness by scratching other stones, they measured density and a special variant of density called specific gravity using scales and jars of water. All these properties are unique to each mineral type and were known long before the chemistry.