(printing, historical) The stone on which the pages or columns of type are imposed or made into forms.

A light, spongy stone, resembling a pumice, used by the ancients in dyeing, and said to be drying and astringent.

(mineralogy) A soft stone used in artistic grinding and polishing, and for cleaning metallic substances. The name is also given to other friable siliceous stones applied to similar uses.

A flint slate used by the ancients to try gold and silver; a touchstone.

(historical) A weight formerly used in Scotland, approximately twenty pounds.

(topology, logic) A topological space constructed from a Boolean algebra, whose points are ultrafilters on the algebra.

A flowering plant, Aethionema grandiflorum.

(obsolete) lapis infernalis, lunar caustic / (obsolete) caustic potash

(obsolete) An imitation jewel or precious stone.

crystal ball