VESU'VIAN, a. Pertaining to Vesuvius, a volcano near Naples.

VESU'VIAN, n. In mineralogy, a subspecies of pyramidical garnet, a mineral found in the vicinity of Vesuvius, classed with the family of garnets; called by Hauy idocrase. It is generally crystallized in four sided prisms, the edges of which are truncated, forming prisms of eight, fourteen or sixteen sides. it sometimes occurs massive. It is composed chiefly of silex, lime and alumin, with a portion of oxyd of iron, and oxyd of manganese.