GIA's Gubelin Gem Project: Garnet

Often thought of as a deep red gemstone, garnet can also be yellow, orange, green or brown – any color except blue. There are six common garnet minerals – almandine, andradite, grossular, pyrope, spessartine and uvarovite – and several rare species. Gem varieties include green demantoid and tsavorite, orangy red hessonite and pink/red rhodolite. Besides brilliance and attractive colors, garnets sometimes exhibit optical phenomena such as asterism (a star-shaped pattern of reflections), chatoyancy (a “cat’s-eye” seen in reflected light), or a color change when viewed under different types of lighting.