CLASSY FELSPAR. 363 Second Kind. Glassy Felspar. Glasiger Feldspath, Werner. Kose, Orthograpliische Briefe, 1. s. 128.—Nbggerath Studicn; s. 27.—Hcuss, Mineralogishe Briefe, 1. n. 2. a. a, o.—Glasi-< gcr Feldspath, Karsten, Tabel. s. 34. Id. Ilaus. s. 88. Id. Steffens, b. i. s. 441. Id. Hoff. b. ii. s. 328. Id. Lenz, b. ii. s. 502. Id. Oken, b. i. s. 375. External Characters. Its colour is greyish-white, sometimes passing into grey. _ It occurs always crystallised, in broad rectangular four-sided prisms, bevelled on the ^extremities. These crystals are often very much cracked; they are generally small, seldom raidddle-sized, and always imbedded. Internally it is splendent., and the lustre is vitreous. The principal fracture is foliated, with the same cleav- age as in adularia: the cross fracture is uneven, or small mid imperfect conchoidal. It is transparent. In all its other characters it agrees with adularia. Specific gravity, 2.575, Klap. 2.518, 2.589, Stuckc. Chemical Characters. Before the blowpipe, it melts without addition into a grey semi-transparent glass. Constituent.
