Vulcanite
a hard and non-elastic variety of vulcanized rubber, used for making combs, dental plates, and numerous other objects. It contains from 30 to 60 per cent. more sulphur, and is subjected to a higher and more prolonged heat in curing than ordinary vulcanized rubber. It is of a brownish-black color, is hard and tough, cuts easily, is susceptible of a good polish, and is not affected by water or any of the other caoutchouc solvents. It evolves a considerable amount of electricity when rubbed, and is hence much used in the construction of electric machines. In petrology, a name sometimes given to pyroxene.