Tophus

n.	1.	(Med.) One of the mineral concretions about the joints, and in other situations, occurring chiefly in gouty persons. They consist usually of urate of sodium; when occurring in the internal organs they are also composed of phosphate of calcium.
	2.	(Min.) Calcareous tufa.

Noun	1.	tophus - a deposit of urates around a joint or in the external ear; diagnostic of advanced or chronic gout Synonyms: chalkstone
	2.	tophus - an incrustation that forms on the teeth and gums Synonyms: calculus, tartar

chalkstone, urate