Bâhr'-stōne, n.

(bûr/stōn), n. [O. Eng. bur, a whetstone for scythes.] (Min.) A variety of flinty quartz, occurring as a rock, and characterized by being very cellular, or irregularly cavernous, in consequence of which it is valuable for mill-stones. Dana. ☞ This word is often written burr-stone.