Garnet. A mineral having many varieties differing in color and in their constituents, but with the same general chemical formula. The commonest color is red; the luster is vitreous, or glassy; and the hardness is greater than that of quartz, about half as hard as the diamond. The common crystal forms are the dodecahedron and trapezohedron. Besides the red varieties there are also white, green, yellow, brown and black ones. The garnet is a silicate with various bases such as alumina-lime (grossularite essonite or cinnamonstone), alumina-magnesia (pyrope), alumina-manganese (spessartite), and chromium-lime (ouvarovite, color emerald green.) The transparent red varieties are used as gems. The garnet was the carbuncle of the ancients. Garnet is a very common mineral in gneiss and mica slate. The finest specimens of red garnets come from Arizona.