Salivary stone of the submandibular gland in a tongue pierced patient.
Sialolithiasis is a term for concrements within the salivary gland ducts. Chemically they consist of calcium phosphates in a carbonated form and other constituents of saliva such as glycosaminoglycans and albumin. In rare cases foreigns bodies can also constitute calculi.
Relevant fotograph: Removed calculus