used for abrasive purposes. Magnetics used in garnet series identification For gem identification purposes, a pick-up response to a strong neodymium magnet separates garnet from all other natural transparent gemstones commonly used in the jewelry trade. Magnetic susceptibility measurements in conjunction with refractive index can be used to distinguish garnet species and varieties, and determine the composition of garnets in terms of percentages of end-member species within an individual gem. Garnet group end member species Pyralspite garnets – aluminium in Y site Almandine: Fe3Al2(SiO4)3 Pyrope: Mg3Al2(SiO4)3 Spessartine: Mn3Al2(SiO4)3 Almandine Almandine, sometimes incorrectly called almandite, is the modern gem known as carbuncle (though originally almost any red gemstone was known by this name). The term "carbuncle" is derived from the Latin meaning "live coal" or burning charcoal. The name Almandine is a corruption of Alabanda, a region in Asia Minor where these stones were cut in ancient times. Chemically, almandine is an iron-aluminium garnet with the formula Fe3Al2(SiO4)3; the deep red transparent stones are often called precious garnet and are used as gemstones (being the most common of the gem garnets). Almandine occurs in metamorphic rocks like mica schists, associated with minerals such as staurolite, kyanite, andalusite, and others. Almandine has nicknames of Oriental garnet, almandine ruby, and carbuncle. Pyrope Pyrope (from the Greek pyrōpós meaning "firelike") is red in color and chemically an aluminium silicate with the formula Mg3Al2(SiO4)3, though the magnesium can be replaced in part by calcium and ferrous iron. The color of pyrope varies from deep red to black. Pyrope and spessartine gemstones have been recovered from the Sloan diamondiferous kimberlites in Colorado, from the Bishop Conglomerate and in a Tertiary age lamprophyre at Cedar Mountain in Wyoming. A variety of pyrope from Macon County, North Carolina is a violet-red shade and has been called rhodolite, Greek for "rose". In chemical composition it may be considered as essentially an isomorphous mixture of pyrope and almandine, in the proportion of two parts pyrope to one part almandine. Pyrope has tradenames some of which are misnomers; Cape ruby, Arizona ruby, California ruby, Rocky Mountain ruby, and Bohemian ruby from the Czech Republic. Pyrope is an indicator mineral for high-pressure rocks. Mantle-derived rocks (peridotites and eclogites) commonly contain a pyrope variety. Spessartine Spessartine or spessartite is manganese aluminium garnet, Mn3Al2(SiO4)3. Its name is derived from Spessart in Bavaria. It occurs most often in skarns, granite pegmatite and allied rock types,