Ruby
Like diamond, sapphire and emerald, rubies are traditionally counted among gemstones. Ruby, like sapphire, is a crystallized form of the mineral corundum. Unlike sapphire, a ruby is always red to pink. Sometimes a pink ruby can also be called pink sapphire. The distinction between these is subjective.
Ruby is one of the hardest materials found in nature and has hardness 9 on the Mohs scale. This makes it very hard-wearing and therefore very suitable for daily wear as jewelry.
The value of ruby depends on its size (carat), color and purity. The most valuable color is "pigeon's blood. Stones with few visible impurities are more valuable, but rubies without inclusions are often extra treated or synthetic.
Almost every ruby is heated before being cut. This improves the color but does not diminish the value.
Rubies are mined on every continent. The main deposits are Kashmir, Myanmar, Thailand and Cambodia.