Volltext Seite (XML)
PORZELLAIfSPATH. 3G1 resinous. e = 1-527. Greyish-white... ash-grey, yellowish and reddish-white. Streak white. Brittle, h = 5'5...6'0. g = 2'4o.. .2*60. Perfectly infusible before the blowpipe. With borax melts slowly into a transparent glass. With soda effervesces and formB a transparent blebby glass. With solution of cobalt becomes blue. In powder is completely decomposed by hydro chloric acid, leaving silica in powder. KSi + AlSi 3 , silica 65‘59, alumina 23'14, potash 21-27. Analyses of leucite a, b from Vesuvius, c from Albano, d from Pompeii, all by Klaproth, e from Vesuvius by Arfvedson, f from Monte Somma by Awdejew :— a b c d e f Silica 63-75 63-50 54 54‘5 60-10 60-05 Alumina 2403 24-25 23 23-5 23-10 2303 Potash 21-35 20-09 22 19’5 21 - 16 20'40 Soda — — — (¥b o-0o) 1-02 Is liable to decomposition, losing its lustre and transparency, and at last falling into powder. In imbedded crystals and grains. Is found in lava near Home at Albano, Nemi, Borghetto, Viterbo, Acquapendente ; in lava around Vesuvius, Monte Somma, Pompeii ; in trachyte between Andemach on the Rhine and the lake of Laacli; in the dolerite of the Kaiser- stuhl in Baden. 201. PORZELLANSPATII.—Porzellanspath; Mohs, Haus- mann, Ilaidinger. Prismatic, mm' = 88°. Cleavage in two directions, at right angles to each other, bisecting the acute and obtuse angles between m, m, not very perfect. Practure uneven. Translucent on the edges. Lustre vitreous, inclining to pearly on the cleavage planes. Yellowish- white, greyish-white, light grey. Brittle. 11 = 5'5. g = 2-06.,.2'08. Phosphoresces when heated. Before the blowpipe melts with intumescence into a blebby colourless glass. Is decomposed by concentrated hydrochloric acid. 3 AlSi + 3CaSi + NaSi 3 , silica 60'8, alumina 28'1, lime 15-0, soda 5-7. B
