Garnet describes any member of a large class of silicate mineral. Their chemical composition varies but may be generally described as X3Y2(SiO4)3. The X and Y locations may be occupied by a variety of elements, such as aluminum and calcium. Garnet occurs in almost all colors, but blue is extremely rare. Its crystal structure may be a cubic or rhombic dodecahedron, belonging to the isometric crystal system. Garnet ranges from 6.5 to 7.5 on the Mohs scale of hardness. Examples of different types of garnets include pyrope, almandine, spessartine, hessonite, tsavorite, uvarovite, and andradite.
Garnets are not traditionally considered precious gems, yet a tsavorite garnet may be even more expensive than a good emerald. Citation