A History of Hindu Chemistry from the Earliest Times to the Middle of the Sixteenth Century A.D. v2.c32.s16.32

v2.c32.s16.32

† Probably refers to dichroism. As has already been pointed out the red ruby and the blue sapphire are only varieties of corundum, which often occur in well-developed crystals belonging to the rhombohedral division of the hexagonal system. "The dichroism of the ruby affords a means whereby it may be distinguished with certainty from other red stones, such as spinel and the different varieties of garnet, which crystallise in the cubic system, and thus being singly refracting can show no dichroism," (Bauer and Spencer). "The dichroism of the sapphires of Siam is specially well marked." —Ibid.