The name 'garnet' refers to a group of minerals related in composition and crystal structure. It occurs in various colours and each has its own name, eg pyrope (red), spessartine (orange), hessonite (brownish red to yellow), rhodolite (pink red), tsavorite (green), demantoid (green), colour-change (green/red). Usually untreated. Birthstone for January. Hardness: 6.5-7.5 (Mohs).