角岩 is read as かくがん (kakugan) and means chert.
かくがん
kakugan
かくせんがん
amphibolite
かくれきがん
breccia
いわかど
edge or corner of a stone
すみ
downstage right (on a noh stage)
かくど
angle
かど
(street) corner
かくかい
the world of sumo
かく
Chinese "horn" constellation (one of the 28 mansions)
つの
horn-like projection (e.g. peaks of whipped cream)
かくざい
squared timber
かくしつ
keratin
かどち
corner lot