novaculite

noun

A very hard, dense, even-textured, silica-bearing sedimentary rock used in whetstones.

A very hard, fine-grained rock, used for hones: same as honestone. It is a very silicious variety of clay slate.

noun

A variety of siliceous slate, of which hones are made; razor stone; Turkey stone; hone stone; whet slate.

noun

A form of chert, very rich in quartz, that has been used to make whetstones