The American Cyclopædia (1879)/Jet

JET, a variety of lignite, resembling cannel coal, but harder, of deeper black, and of more brilliant lustre. It is found in detached pieces in tertiary clays along the coast of Yorkshire, England, and in various places on the continent of Europe. From its susceptibility of taking a fine polish and its intense blackness, it has been largely used for mourning articles of ornament, as buttons, crosses, and ear rings.