Almandine is naturally occurring mineral, a species of the garnet group, chemically a silicate of the metals iron (bivalent) and aluminum (Fe3Al2Si3O12). Its crystal system is isometric, the crystal habit often being well-developed rhombic dodecahedral shapes, colored a characteristic brownish-red. It occurs in schists and other metamorphic rocks as seen in this sample from near Lake Martin in Alabama, USA, and actual width 130 mm.