300 DESCRIPTIONS OF MINERALS. 



of thin slices, it has been suspected to be dimetric like 

 leucite, or else trimetric like phillipsite, although the forms 

 of the crystals are apparently isometric. Often colorless 

 and transparent, also milk-white, grayish and reddish- 

 white, and sometimes opaque. Lustre vitreous. H. = 5-5-5. 

 G.=2 25. 



Composition. Na 2 Al Oi 2 Si 4 4- 2aq = Silica 5447, alumina 

 23-29, soda 14-07, water 8-17 = 100. B.B. fuses easily to a 

 colorless glass. Decomposed by hydrochloric acid ; and the 

 silica separates in gelatinous lumps. 



Biff. Characterized by its crystallization, without cleav- 

 age. Distinguished from quartz and leucite by giving water 

 in a closed glass tube ; from calcite by its fusibility, and by 

 not effervescing with acids ; from chabazite and its varieties 

 by fusing without intumescence to a glassy globule, and by 

 the crystalline form. 



Obs. Pound in cavities and seams in amygdaloidal trap, 

 basalt and other eruptive rocks, and sometimes in granite, 

 syeuyte and gneiss. 



Occurs in fine crystallizations in Nova Scotia ; also at 

 Bergen Hill, N. J. ; Perry, Me. ; and in the trap of the Cop- 

 per region, Lake Superior. The Faroe Islands, Iceland ; 

 Glen Parg, near Edinburgh ; Kilmalcolm, the Campsie 

 Hills, and Antrim ; the Vicentine ; the Hartz at Andreas- 

 berg ; Sicily, and Vesuvius, are some of the foreign localities. 



The name analcite is from the Greek, analhis, weak, al- 

 luding to its w^eak electric power when heated or rubbed. 



EudnopMte. Near analcite. From Norway. 



Faujasite. In isometric octahedrons. From the Kaiserstuhl, Baden. 



Chabazite. 



Khombohedral. Often in rhombohedrons, much resem- 

 bling cubes. R : 72=94° 46'. Cleavage parallel to 

 i?. Also in complex modifications of this form. 

 Never massive or fibrous. 



Color white, also yellowish, and flesh-red or red. 

 Lustre vitreous. Transparent to translucent. H. = 

 4-5. G. =2 -08-2 -19. 



The red chabazite of Xova Scotia has been called Acacli- 

 alite. 



Composition. CaAd 12 Si 4 + 6aq, with a little Xa 2 or K 2 in 

 place of part of the Ca. The Xova Scotia acadialite afforded 



