(A) A building stone of a grey colour. (b) Geology. A grey volcanic rock composed of feldspar (sometimes replaced by leucite or melilite) and augite or hornblende (now chiefly historical).
Origin
Late 18th century. From grey + stone.
Definition of greystone in US English:
greystone
nounˈɡreɪstəʊn
(A) A building stone of a grey colour. (b) Geology. A grey volcanic rock composed of feldspar (sometimes replaced by leucite or melilite) and augite or hornblende (now chiefly historical).