A mineral having many varieties differing in color and in their constituents, but with the same crystallization (isometric), and conforming to the same general chemical formula. The commonest color is red, the luster is vitreous, and the hardness greater than that of quartz. The dodecahedron and trapezohedron are the common forms.
- Any of several common, widespread aluminum or calcium silicate minerals occurring in two internally isomorphic series, (Mg, Mn, Fe)3Al2Si3O12 and Ca3(Cr, Al, Fe)2Si3O12, generally crystallized, often embedded in igneous and metamorphic rocks, and colored red, brown, black, green, yellow, or white and used both as gemstones and as abrasives.
- A dark to very dark red.
- Nautical A tackle for hoisting light cargo.