HYDROUS SILICATES—GENERAL SECTION, 293 
I. GENERAL SECTION, 
Pectolite. 
Monoclinic, isomorphous with wollastonite. Usually in 
agoregations of acicular crystals, or fibrous-massiye, radiate, 
stellate. Color white, or grayish. ‘Translucent to opaque. 
iowelt.. “U5. G.= 268-28. 
Composition. RO;Si, in which R=+4H, tNa, 4Ca, = Silica 
a). lume Ba:s, soda 9:3, water 2°7=100. In ‘the closed 
tube yields water. B.B. easily fusible. Decomposed by hydro- 
chloric acid, and the solution gelatinizes somewhat when 
evaporated. 
Dif. Its fibrous forms and its blowpipe reactions are 
distinctive. 
Obs. Occurs mostly in cavities or seams in trap or basic 
eruptive rocks, and occasionally in other rocks: Found 
at Ratho Quarry, near Edinburgh, Scotland; at Kilsyth ; 
Isle of Skye ; in the Tyrol; in fine specimens at Bergen 
Hill, N. J.;.a compact variety at Isle Royale, Lake Supe- 
rior. | ; 
Okeniéc and Gyrolite are related hydrous calcium silicates. Okenite 
is from the Faroe Islands, Iceland, and Greenland, and gyrolite from 
the Isle of Skye, and frqgm Nova Scotia 25 miles southwest of Cape 
Blomidon. 
(ymatolite. White, curved-fibrous (to which the name from the 
Greek kuma, wave, alludes), vitreo-pearly, with G.=2-°74. Analysis 
afforded Silica 61°21, alumina 28°01, potassium 4°54, water 3 83, with 
about half a per cent. each of lime, soda, and lithia, making ita hydrous 
bisilicate, if half the water be made basic. Derived trom the altera- 
tion of spodumene. Occurs at Goshen and Norwich, Mass., and Red- 
ding, Conn. At the latter place crystals of spodumene of great size 
are converted into it. 
Laumontite. 
“Monoclinic, with the angles nearly of pyroxene ; 7A J= 
86° 16". Cleavage parallel to the clinodiagonal section and 
to I perfect. Also massive, with a radiating or divergent 
structure. 
Color white, passing into yellow or gray, sometimes red. 
Lustre vitreous, inclining to pearly on the cleavage face. 
igansparent vo translucent. H.=35—4.  G@.=2-25-2°36. 
Becomes opaque on exposure through loss of water, and 
readily crumbles. } : 
Composition. CaAlO,.Si,+4aq=Silica 50:0, alumina 
21°8, lime 11°9, water 163=100. B.B. sweils up and fuses 
