Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/432

414 MINERALOGY 532. PENNINE, 4MgSi + Mg.jAl + 5H . Hexagonal, rhombohedral ; R 65 28 . Crystals chiefly very acute rhombonedrems, with or without the base. Lustre resinous. H. = 2 to 3; G. =2 6 to 277. Streak greenish white. B.B. exfoliates, becomes white, and fuses on the edges to a white enamel. Com pletely sol. in warm s. acid. C.c. : 33 6 silica, 14 4 alumina, 39 4 magnesia, and 12 6 water; but with 5 to 6 iron protoxide re placing magnesia. Scalpa in Harris, Glen Lochy in Perthshire, Zcnnatt in Valais, Tyrol, Ala di Stura in Piedmont, Mauleon in the Pyrenees. Lcuchtcnbergite is the same. Kammererite, with 5 to 8 chromium sesquioxide, is violet-blue or green ; Unst, Siberia, Pennsylvania. Rhodochrome and Tabcrgite are also varieties. 533. CLINOCHLORE (Eipidolite), 3MgSi + Mg 3 Al + 4fi . Oblique prismatic, C. 76 4 . ooP 121 28 . OP : P 113 59 ; OP : oo P 192 8 . Crystals - 2P, P, 4P c oo , OP (n, m, t, P, fig. 494). Twins common ; lustre vitreous or resinous. H. =2 to 3; G. =2 6 to 2 8. B.B. becomes white, and fuses on thin edges to a greyish yellow enamel. C.c. : 30 3 silica, 17 3 alumina, 40 - 3 magnesia, and 12 1 water. Edentian and Blair Athole in Scotland, Traversella in Piedmont, Akhmatovsk in Urals, West Chester in Pennsylvania. Corundophyllite, Epi- < chlorite, and Kotschubcyite are varieties. 534. PYROSCLERITE, (fK, R-) 3 Si 3 + 3fi . Fig. 494. Right prismatic. Cl. basal, perfect ; fracture uneven ; brittle ; sectile. H. =3; G. =27 to 2 "8. Pearly; translucent. Apple-, emerald-, and grey-green. C.c.: alumina 13 4, chrome oxide 1 4, protoxide ofiron3 5, magnesia 31 6, silica 37, water 11. Porto- Ferraio in Elba, China. 535. CHONICRITE. Massive ; crystalline-granular and globular-radiated. H. = 2 - 5 to 3 ; G. =2 "91. Weak silky. White, with yellowish spots ; greenish blue. C.c. : 17 1 alumina, 22 6 magnesia, 12 6 lime, 357 silica, 9 water. B.B. fuses easily, with intumescence, to a grey glass. De composed by h. acid, with separation of silica. Colmouell (Ayrshire), Porto-Ferraio. 536. PYONOTROP. Large grained aggregates. Cl. along two rectangular faces ; frac ture hackly, splintery. Greyish white to brown-red. Vitreous to greasy. H. =2 to 2 3 ; G. =2 6 to 27. C.c.: alumina 29 3, mag nesia 12 6, potash 4 - 4, silica 45, water 7 "8. Waldheim in Saxony. 537. THURINGITE, (%R, fi 3 + $(Al, Fe)) 4 Si 3 + 4H. Massive ; scaly. H. = 2 to 2 5 ; G. = 3 "2. Pearly. Olive-green to pistachio-green ; streak paler. Very tough. Powder greasy. C.c.: alumina 16, peroxide of iron 14, protoxide of iron 33, silica 23, water 11. Schmiedefeld in Thuringia, Harper s Ferry on the Potomac, Hot Springs in Arkansas. 538. DELESSITE, (Fe|, Mgf) 2 Si 2 + (Al T V, Fe T 9 Tr )Si + 3ft + 2Mgfi. Massive ; scaly. H. =2 to 2 "5 ; G. -2 6 to 2*89. Olive-green to dark green, passing to dark brick-red ; streak light green. C.c.: alumina 16 3, protoxide of iron 12 6, magnesia 21, silica 31 5, water 15 - S. Common in igneous rocks of Old Red Sandstone and Coal- measure age in Scotland. Oberstein, Zwickau, Lagreve near Mielin. 539. CRONSTEDTITE, FeSi + (Fe, Mg) 3 Si + 3fi . Rhombohedral; radiated columnar. In tapering hexagons, and hemihedral (figs. Fl S- 495 - (Sp.689.) Fig.496. 495, 496). Cl. basal, perfect; elastic. H. = 2 5 ; G. = 3 3 to 3 5. Vitreous. Coul-black and brownish black; streak dark olive-green. C.c. : protoxide of iron 39, peroxide of iron 29, silica 22, water 11. Huel Maudlin in Cornwall, Przibram, Brazil (Sideroschisolite). TALC AND SERPENTINE GROUP. 540. TALC, Mg ;1 Si 4 + H. Right prismatic (?) ; rarely found in six-sided or rhombic tables ; generally massive, granular, or scaly. Rarely fibrous. Cl. basal, perfect; soft, sectile, and flexible in thin plates. H. =1; G. =2 6 to 2 - 8. Transparent in thin plates, and optically binaxal ; pearly or resinous. Colourless, but generally greenish or yellowish white to apple- or olive-green. Feels very greasy. B.B. emits a bright luht, exfoliates, and hardens (H. =6), but is infusible ; with cobalt solution becomes red. Not sol. in h. or s. acid before or after igni tion. C.c. : 63 5 silica, 317 magnesia, and 4 8 water. Unst in Shetland, green ; Cairnie in Aberdeenshire, brown ; Greiner in Tyrol, Sala and Falun, the Pyrenees. Used as crayons, also for forming crucibles and for porcelain. Steatite. Massive. Grey, red, yellow, or green. Shetland, Sutherland, Portsoy, and near Kirkcaldy, Scotland ; the Lizard Point, Cornwall ; Briancon, Wunsiedel. Savage nations cut the steatite into culinary utensils. Potstone is a mixture of talc, chlorite, and other minerals. 541. PICROPHYLL, 3RSi + 2H. Right prismatic. H. =2 5 ; G. =375. Dark green. Foliated, shining. C.c.: magnesia 30 1, protoxide of iron 6 9, silica 49 8, water 9 8. Sala in Sweden. 542. PICROSMINE, 2MgSi + H . Right prismatic, but massive. Cl. ooPoo perfect, less so in other directions ; sectile. H. = 2 5 to 3 ; G. =2 5 to 27. Translucent or opaque ; vitreous, but pearly on ooPoo . Greenish white, grey, or blackish green ; streak colourless. Yields a bitter odour when breathed on ; hence the name. C.c.: 55 8 silica, 36 1 magnesia, and 8 1 water. Presnitz in Bohemia, and Greiner in Tyrol. 543. MONRADITE, 4(| Mg, Fe)Si + H . Massive, foliated, translucent, and yellowish -grey. H. =6 ; G. = 3 27. C.c. : silica 55 2, magnesia 31 "9, protoxide of iron 8 8, water 4 1. B.B. infusible. Bergen in Norway. 544. MEERSCHAUM, 2Mg.,Si 3 + 4H-. Fracture earthy; sectile. H. =2 to 2 5 ; G. =0 - 8 to 1 (when moist nearly 2). Opaque, dull. Yellowish and greyish white; streak slightly shining. Feels rather greasy, and adheres strongly to the tongue. C.c. : 54 2 silica, 24 7 magnesia, and from 9 to 21 7 water. Negropont, Anatolia, near Madrid and Toledo, Moravia, Werm- laud. 545. APHRODITE, 4MgSi + fi. Soft and earth} . G. =2 21. Milk-white; opaque. C.c.: 52 9 silica, 35 3 magnesia, 11 9 water. Laugban (Sweden), Elba. 546. SPADAITE, Mg 5 Si 6 + 4H. Massive; fracture splintery ; sectile. H. =2 5. Translucent; resinous. Red, with white streak. C.c.: 57 silica, 31 - 6 magnesia, 11 "4 water. Capo di Bove near Rome. 547. GYMNITE. Massive. H.=2to 3; G. =! 9to2 i 2. Translucent; resinous. Dull orange-yellow. C.c.: 41 silica, 37 magnesia, 22 water. Tyrol, Passati, Texas, Barehills near Baltimore. Nickel Gymnitc has 29 of nickel oxide, replacing the water. Unst, Texas, Pennsylvania. 548. SAPONITE, (FeCaMg) 6 Si 6 + (Al 3 Fe)Si+ 13ft . Massive ; sectile, and very soft. H. = 1 5 ; G. = 2 2 to 2 3. White, orange-yellow, pale green, and reddish brown. Feels greasy ; does not adhere to the tongue ; falls to pieces in water. C.c.: silica 40 8, alumina 7 5, ferric oxide 3 "9, magnesia 20 6, water 227. Occurs in all the above colours in the later igneous rocks of Scotland, com monly. Lizard Point and St Clear in Cornwall, and Dalecarlia in Sweden. Pimelite has 2 - 8 oxide of nickel. 549. SERPENTINE, 2MgSi + MgH 3 . Crystallization uncertain ; pseudomorphic after olivine, &c. ; generally massive, and granular or fibrous ; fracture flat-con- choidal, uneven, or splintery ; sectile, and slightly brittle. H. =3 to 3 5 ; G. =2 5 to 27. Translucent to opaque ; dull resin ous. Green, grey, yellow, red, or brown; often in spots, stripes, or veins ; streak white, shining. Feels greasy, and does not adhere to the tongue. In the closed tube yields water, and becomes black. C.c. : 43 5 silica, 43 - 5 magnesia, and 13 water ; but with 1 to 8 iron protoxide, and also carbonic acid, bitumen, and chrome oxide. Varieties are (1) Noble Serpentine, brighter coloured, 16H 0, and more translucent; (2) Picrolite, or fibrous (H. =3 5 to 4 5) ; (S) Common, or compact; (4) Chrysotilc (Baltimorite, Mctaxite), in fine asbestiform fibres, easily separated, with a metallic or silky lustre (G. =2-219). Common in Shetland, Urquhart, Portsoy, Ballantrae ; Lizard Point in Cornwall ; Norway, Sweden, North America. Chrysotile at Colafirth and Fetlar, Shetland, Portsoy, Towanreiff, in Scot land; Reichenstein in Silesia, the Vosgcs Mountains, and North America. Serpentine is often a product of decomposition, or psendo- morph of various minerals, as augitc, hornblende, olivine, spinel, enstatite, garnet, &c. It forms whole rocks and mountains, and is manufactured into various ornamental articles. 550. MARMOLITE, 3MgSi + 2MgH., . Oblique prismatic; often foliated. H.=2 5 to 3; G. =2 41 to- 2 - 47. Lustre pearly. Greenish white, bluish white, and asparagus- green. C.c. : silica 42 1, magnesia 38 5, water 17 5. In veins in serpentine of Urquhart and Portsoy (Scotland) Cornwall, Fin land, Hoboken. 551. ANTIGORITE. Thin flat lamhue. H. =2 5 ; G. =2 6. Translucent. Green with brown spots ; streak white. C.c.: silica 40 8, magnesia 36 3, prot

oxide of iron 5 8, water 12 4. Antigorio in Piedmont.