Pumice Is

Pumice is:

A) frequently found in block form, which is then run onto a rag wheel to polish precious and semiprecious metal alloys in the laboratory
B) used in coated disks and bonded rotary devices primarily used in finishing procedures
C) a major component of many prophylaxis pastes used to polish tooth structure, dental amalgam, and acrylic bases
D) used to smooth enamel, or finish metal alloys and ceramic materials