"Talc (magnesium silicate) is used in the preparation of tablets intended for oral use, where it acts as a 'filler' and lubricant. When these tablets are ground down, dissolved and injected for illicit use, the talc accumulates in the pulmonary circulation. These deposits result in small foreign body reaction granulomas, which are birefringent under polarised light. If use is persistent the nodules can coalesce to form larger masses."