UNISILICATES. 269 



I) iff. Its square prisms and the angle of the pyramid at 

 summit are characteristic. In cleavable masses it resembles 

 feldspar, but there is a slight fibrous appearance often dis- 

 tinguished on the cleavage surface of scapolite, which is 

 peculiar. It is more fusible than feldspar, and has higher 

 specific gravity. Spodumene has a much higher specific 

 gravity, and differs in its action before the blowpipe. Tabu- 

 lar spar is more fibrous in the appearance of the surface, 

 and is less hard ; it also gelatinizes with acids. 



Obs. Found mostly in the older crystalline rocks, and also 

 in some volcanic rocks. It is especially common in granular 

 limestone. Fine crystals occur at Gouverneur, N. Y., and 

 at Two Ponds and Amity, N. Y.; at Bolton, Boxborough 

 and Littleton, Mass. ; at Franklin and Newton, N. J. It 

 occurs massive at Marlboro', Vt. ; Westfield, Mass. ; Monroe, 

 Ct. Foreign localities are at Arendal, Norway ; Wiirmland, 

 Sweden ; Pagas in Finland, and also at Vesuvius, whence 

 come the small crystals called meionite. 



Nuttallite, Glaucolite, are varieties of this species. 



Ekebergite resembles wernerite, being distinguishable from it only 

 by chemical analysis. Dipyre also is near wernerite, but contains 

 more silica and 10 per cent, of soda ; from the Pyrenees. 



Meionite, a lime scapolite, is like wernerite in its crystals, but has 

 the formula (^Ca|Al) 2 12 Si 3 , being a true unisilicate. From Monte 

 Somma. 



Mizzonite and Marialite resemble meionite. Paranthine and Sar- 

 colite are other related unisilicate species. 



Nephelite. — Nepheline. 



Hexagonal. In hexagonal prisms with replaced basal 

 edges ; Oa1~135° 55'. Also massive ; sometimes thin col- 

 umnar. 



Color white, or gray, yellowish, greenish, bluish -red. 

 Lustre vitreous or greasy. Transparent to opaque. H. = 

 5-5-6. G. =2-5-2-65. 



Composition. (Na,, K 2 )A10 8 Si 2 = (if Na : K=5 : 1) Sili- 

 ca 44-2, alumina 33-7, soda 16-9, potash 5*2 = 100; a little 

 lime is usually present. B.B. fuses quietly to a colorless 

 glass. Decomposed by hydrochloric acid, and the solution 

 gelatinizes on evaporation. The name nephelite alludes to 

 the mineral becoming clouded in acid. Nephelite includes 

 the glassy crystals from Vesuvius called Sommite, and also 

 hexagonal crystals in other volcanic rocks ; and a massive 

 variety, of greasy lustre, called Elceolite, from the Greek 



