Sapphire

This is a picture of a cabochon star sapphire. Although a lot of people associate sapphire with the color blue, sapphire comes in all colors of the rainbow except for red. My roommate recently got engaged and her fiancé gave her a yellow sapphire wedding ring. A little different than your average run of the mill engagement ring but very beautiful and classy. Just like her! 
When I was learning about gemology, I was suprised to find out that ruby has the same chemical makeup as sapphire. The only thing that distinguishes a ruby from a sapphire is its color. If a sapphire is red, it is a ruby. Ruby and sapphire come from the mineral family corundum and have a mohs hardness of nine. This is only one less than the hardness of diamonds. So, the only stone other than a sapphire that could make a scratch on a sapphire is a diamond. Also, sapphires are very durable. Maybe that's why they are often used as watch faces.