Bead, Garnet (natural), 5mm smooth Heishi, C grade Mohs hardness 6.5-7.5, Sold per 14 inch strand Garnets /???rn?t/ are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. Garnets /???rn?t/ are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives.The different species are pyrope, almandine, spessartine, grossular (varieties of which are hessonite or cinnamon-stone and tsavorite), uvarovite and andradite.