Jet, a black inflammable concrete, which becomes electrical by friction; attracts light substances, in the same manner as amber, and, when burning, emits a bituminous smell. It has the grain of wood, is but moderately Hard, and splits most easily in a horizontal direction.

Jet is always found in detached masses, lodged in other strata; it abounds no where so plentifully as in England, being very common in Yorkshire, and other northern counties, though it is also discovered in many clay-pits about London. Ireland, Sweden, Prussia, Germany, and other parts of Europe, as well as the East Indies, produce this fossil. It admits of a high polish, and is chiefly converted into small boxes, buttons, bracelets, and other toys. In conjunction with oils, it forms an ingredient in varnishes; and, when mixed with pulverized lime, it is said to produce a hard and durable cement.