Jet
Jet, a compact, black form of lignite (a type of coal). Jet is very durable, takes a high polish, and can readily be carved into buttons, toys, and jewelry. For most purposes, however, jet has been replaced by black onyx, an artificially colored form of chalcedony.
Jet has been known since prehistoric times. The early Greeks used powdered jet mixed with wine as a remedy for toothache and jet mixed with beeswax as a treatment for tumors. The finest jet is found in thick veins near Whitby, England. The abbey of Whitby did a thriving business in jet rosaries and crucifixes during the seventh and eighth centuries.