Spessartite garnet is the most famous orange gem, but there are a number of other options as well. Orange sapphire is produced by heat treatment. The finer fire opal occurs in hues from yellow-orange to red-orange. Natural fancy orange diamonds are caused by the presence of nitrogen in the diamond's carbon lattice structure.
Some orange gemstones include: Spessartite Garnet, Orange Diamond, Andesine, Zircon, Fire Opal, Orange Sapphire, Orange Tourmaline, Imperial Topaz, Mandarine Garnet, Mali Garnet, and Citrine