CORUNDUM. 43 The fracture is perfect foliated, with a four-fold clea vage. Three of the cleavages are parallel with the trun cating planes on the alternate angles of the six-sided prism, and the fourth with the terminal planes of the prism. The cross fracture is small, and imperfect con- choidal. The fragments are rhomboidal. It shews a tendency to straight lamellar concretions. It alternates from translucent to translucent on the edges, and it refracts double. It is so hard as to scratch quartz; but is softer than sapphire. It is rather easily frangible. Is rather heavy, approaching to heavy. Specific gravity 3.710, Klaproth.—3.873, Hany.— 3.875, Bournon. Constituent Parts. Corundum of the Carnatic. Of Malabar. Diamond spar, or Corundum of Chinn.- Alumina, - 91.0 86.5 84.0 Silica, - 5.0 7.0 6.50 Iron, - 1.5 4.0 7.50 Toss, - 2.5 2.5 2. 100 100 100 Chenevix. Klaproth. Geognostic Situation. In India, it occurs imbedded in a rock composed of felspar, fibrolite, quartz, hornblende, and mica, and is sometimes accompanied with pistaCite, talc, garnet, and zircon. In Italy, it is imbedded in mica-slate. Geographic