Garnet
Garnets are a group of closely related minerals that come in almost every color. The most famous and common are the red spessartite and rhodolite garnets but almost any color is available. Among the rarer types is tsavorite which is a beautiful green.
Garnet is the birthstone for January
Mineral: Garnet group
Refractive index: 1.714 - 1.888
Specific gravity: 3.47 - 4.15
MOHS Hardness: 6.5-7.5