Natural Red Rhodolite Garnet Faceted Marquise Drops Length is 4.5 Inches & Sizes from 9mm to 10mm Approx. 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.