Garnet is the name of a group of silicate minerals with the general formula A 3 B 2 (SiO 4) 3, the six common garnets being almandine (Fe,Al), grossular (Ca,Al), pyrope (Mg,Al), spessartine (Mn,Al), andradite (Ca,Fe), and uvarovite (Ca,Cr).. All garnets are hard (6.5–7.5 on the Mohs scale), resistant to degradation caused by physical abrasion and chemical attack, and have relatively high ...