Hardness, 10, Moh’s scale.
Specific gravity. 3.48 to 3.52. (Carbonado, 3.14 to 3.41.)
Index of refraction. 2.439.
Singly refractive, reflective and dispersive.
Total reflection from inner facets at 24° 15°. Composition: pure carbon.
Cleavage perfect, parallel to the facets of the octahedra. Fracture, conchoidal.
Streak, gray to black : the finer the material the darker the powder.
Luster, adamantine. Transparent.
Phosphoresces in the presence of radium; occasionally after exposure to heat or solar light.
Electric in the rough. Though a nonconductor, it be-comes positively electric, by friction.
Infusible, not acted upon by acids or alkalies, but burns in oxygen under intense heat without appreciable residue to carbon dioxide.
Colors, white and with tints of blue, yellow, brown, green, and pink. Also in red, green, blue, yellow, brown, and orange of decided color.
Common imperfections, carbon spots, inclusions of titanic iron, etc., fractures, feathers, bubbles and white specks.
Occurs in South Africa, Brazil, India, Borneo, Sumatra, British and Dutch Guiana, Australia, Russia, China, and the United States.
Bort comes principally from Africa, and carbonado from Brazil only.
Symbolizes purity, preserves peace, prevents storms; the month of April.
Third stone of the second row in the Jewish High Priest’s breastplate.