Hardness, 10, Moh's scale.
Specific gravity. 3.48 to 3.52. (Carbonado, 3.14 to
Index of refraction. 2.439. Singly refractive, reflective and
dispersive. Total reflection from inner facets at 24 ° 15'.
Composition: pure carbon. Crystallization. Isometric.
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
exposure to heat or solar light. Electric in the rough. Though a
nonconductor, it becomes 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.