( 33 1 ) , nineteenth species. Whet Slate, W etzfchiefer.—Werner. hiftus coticula, Will, t. x. p. 353.—Wetzcliiefer, Wid. P- 402—Novaculite, Kirw. vol. 1. p. 238. —Wetzi chiefer, Eftner, b. 2. f. 664. Id. Emm. b. x. ^305— •etra cote, Nap. p. 270—Cos. Lam. t. 2. p7 105 — e fchifte a aiguifer, Broch, t. I. p. 393.—Argile fchif- Ufe n °vaculaire, Hauy, t. 4. p. 448. External Characters. a j^ ts common colour is greenifh grey, it occurs mountain, afpaiagus, olive, and oil green. Mafiive. ( ^ternally weakly glimmering, almofl: dull. r a ure is in the large flaty, in the fmall fplintery. r ra gments tabular, iranflucent on the edges. e mihard, palling into foft. e els rather greafy. 0t Particularly brittle. Not