Spessartite is synonymous with spessartine, though in the gem trade Spessartite is more frequently used (the name a derivative of Spessart in Baravia, Germany, the type locality of the mineral) and is the manganese aluminium species of the silicate mineral group, Garnet.
Natural spessartite has an orange colour, but iron impurities are usually present which give it a reddish-orange or brownish-orange colour. Pure orange spessartite is not common; red, brown or yellow tints are frequent. Its most desirable colour is a fiery-red with slight orange tints. It has an exceptionally high refractive index giving cut spessartite gemstones a special brilliance.
Once a fairly uncommon specimen, many new deposits of facetable spessartite crystals with excellent colour have been discovered making this form of garnet more readily available.
One very important deposit was discovered in the 1960's in the Umba River Valley of Tanzania and Kenya. Although not pure spessartites, they were given the trade name Malaya Garnets. Spessartites of an orange-yellow have been called Mandarin garnet and are found in Madagascar. Violet-red spessartites are found in Colourado and Maine. Spessartites form a solid solution series with the garnet species almandine. Well formed crystals of this series, varying in colour from very dark-red to bright yellow-orange, were found in Latinka, Rhodope Mountains, Bulgaria.
It occurs most often in granite pegmatite and allied rock types and in certain low grade metamorphic phyllites. Sources include Australia, Myanmar, India, Afghanistan, Israel, Madagascar, Tanzania and the United States.