Bĭ-tū'men, n.

n. [Lat. bitumen, Fr. & It. bitume, Pg. betume, Pr. betum, Sp. betun.] Mineral pitch, a substance having a pitch-like odor, and burning readily with a bright flame, without any residue. There are many varieties, from liquid naphtha to the solid asphaltum.

☞ Naphtha is a clear, yellowish liquid: petroleum and mattha are more viscid and of a much darker color; asphaltum is solid and brittle, having often a bright conchoidal fracture. The liquid kinds come out from bituminous rocks, or from clay beds containing coal or lignite. The liquid pitch often rises to the surface along with the waters of springs. The solid kinds proceed from the hardening of the softer by evaporation of volatile parts.