Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/440

Rh 422 MINERALOGY (figs. 554, 556). Faces of P striated parallel to the polar edge, those of the prism horizontally (fig. 555). Cl. o&amp;gt;P distinct. Gelatinizes Fig. 556. with h. acid. C.c. : 47 6 silica, 197 alumina, 12 soda, 207 water. Certain crystals seem to indicate twinning. Talisker in Skye (twins of fig. 555), Glenarm in Antrim (fig. 555), Vicenza, Pyrgo in Cyprus, Cape Blomidon in Nova Scotia. 610. LEVYNE, AlSi., + CaSi + H5. Rhomboh ^ ; R (s) 79 29 ; - R (r) 1 3 ; OR (p). Forms intersecting twins as in fig. 557. H. = 4 ; G. = 2 -1 to 2 -2. Colourless Fig. 557. and white. C.c. : silica 43 8, alumina 23 8, lime 97, water 21. Storr in Skye (o, s), Ireland (at Glenarm, Island Magee, London derry, &c.), Iceland, Dalsnypen and Naalso in the Faroes. 611. + Fig. 558 (sp. 611). Aci- HEE.SCHELITE, (CaNa)Si + 5H. Hexagonal prisms (e) surmounted by two trihedral pyramids of a 7 and one of V( fi g- 558). 7 :el228 ; a^- : e 107 26 ; e striated hori zontally. Cl. e ; fracture con- choidal ; transparent ; vitreous. White or colourless. H. =5 5; G. =2 06. C.c. : silica 47, alu mina 21 2, lime 5 - 2, soda 4 - 8, potash 2, water 17 Castello and Palagonia in Sicily, Yarra in Australia. 612. LAUMONTITE (Leonhardite), AlSi 3 + CaSi + 4H. Oblique prismatic, C 80 42. ooP (m) 8& 16. o&amp;gt;P : - cop ( e ) 113 30 ;Poo (a;.,):- ooP 111 14 ; e : a 125 41 ; a : b 90 ; e : z 149 15. Twin face a. Cl. m, perfect; very brittle. H. =3 to 3 5 ; G. =2 2 to 2 3. Pellucid when fresh ; vitreous ; pearly White, cream-coloured, brick-red. De- on cl. composes rapidly through loss of water. B. B. intumesces, and melts first to a white enamel, ultimately to a clear glass. Gelatinizes in h. acid. C.c: silica 50 9, alumina 21 8, lime 11 9, water 16 3. Rapidly loses 1 equivalent or 3 86 per cent, of water, and becomes fri able (Hypostillitc}. Kilfinichen, Mull (fig. 559) ; Storr and Quiraing, Skye (hypostil- bite) ; Tod Head, Snizort, Glen Farg (red) ; Bowling, Dumbarton (twins of m, e) ; Huel- oat in JJrittany ; Prague, Falun, Iceland, Fig. 559. Faroes, Nova Scotia. water. Caportianite from Tuscany has only 3 613. EPISTILBITE (Reissite), Oblique prismatic, C 54 53 . oo P (m) 135 10 ; Poo (t) 109 46 ; |P(s)14740 (fig.560). Hemi- tropes united by m, with twins of the same united by the brachy- diagonal (a). Cl. brachydiagonal, perfect. H. = 3 5 to 4; G. = 2 3 to 2 &quot;4. Pellucid ; vitreous ; pearly on cl. Colourless. Sol. without gelatinizing. C.c. : silica 59, alum ina 17 5, lime 9, soda 1 5, water 14 5. Talisker in Skye (m, t, a); Hurtlepool (in twins), Iceland, Faroes, Silesia, Viesch in Valais, Nova Scotia, and New Jersey. 614. HEULANDITE, AlSi 3 + CaSi., + 5& . Oblique prismatic, C 63 40 . Poo (&amp;gt;) 50 20 ; 2P (z) ; f P (u} , 2P c o (r) ; 3Pcoo (s) ; cc Crystals elongated along each of the axes pre sent very varying forms, but generally tabular Cl. clinodiagonal, per fect ; pearly on this, vitreous on others ; brittle. H. =3 5 to 4; G. =21 to 2 -2. Trans parent to translucent ; colourless, white, brick- red, rose, green, hair- brown. B. B, melts with exfoliation and intu mescence to a white enamel. Sol. in h. acid, leaving silica. Storr and Talisker, Skye (fig. 562) ; Sanda ; Kilmalcolm ; Catteiiine, Kincardine (fig. 563); Kilpatrick Hills (p, m, n, z, u, r, s) and Kintyre (red) ; Iceland, Faroes, o&amp;gt;P c ; OP. z : z 136 4 ; u : u 146 52. Fig. 565. Fig. 564. Fassa Valley, Nova Scotia, Baltimore (Beaumontite) (fig. 565) (p, m, n, z, t) ; Vindhya Mountains in India (fig. 564). 615. BREWSTERITE, A-Vs i 3 + RSi 3 + 5H. K = (Sr + Ba + } Ca). Oblique prismatic, C 86 56. &amp;lt;xPoo (a) ; ooP oo (I) OP (o) ; %P c oo (e); ooP (m); ooP2 (c); ooP f (t). e:e 173 10 (fig. 566). Cl. clinodiagonal, perfect ; pearl} 7 on do., vitreous on others; pellucid. H. =5 to 5-5; G. = 2 5 to 2 -45. Colourless, yellow, or brown. Sol. with gelatinization in h. acid. C.c. : 54 &quot;3 silica, 15 alumina, 9 strontia, 6 6 baryta, 1 3 lime, 13 5 water. Strontian, Freiburg in the Breisgau, Pyrenees. 616. PHILLIPSITE, AlSi 3 + (Ca, K)Si + 5H. Oblique prismatic, C 55 1. ooP (m) ; ooP c oo (&) ; OP (c). Polar edges 120 42 and 119 18 . Faces b and in striated parallel to the intersections. Apparently always twinned; generally these duplicated by intersection on face b or face c (figs. 567, 568), and frequently J - ^ 565 ^ S P- 615 ) arranged so that three of the above double twins intersect at right angles to one another, forming the cruciform fig. 569. Fig. 569. Fig. 570. When the prismatic faces of these are short, the faces m of the