294 



DESCRIPTIONS OF MINERALS. 



Obs. Found in the veins and cavities of trap rocks and 

 also in gneiss, porphyry. Occurs at the Faroe Islands ; Kil- 

 patrick Hills, near Glasgow ; Disco, Greenland ; St. Goth- 

 ard, Switzerland ; Peter's Point, Nova Scotia ; Phippsburg, 

 Me.; Oharlestown syenite quarries, Mass. ; Bergen Hill, 

 X. J. ; the Copper region, Lake Superior, and Isle Rovale. 



Leoiihardite. Probably Laurnontite which has lost part of its water 

 by alteration. It resembles that species in crystallization and in most 

 of its characters, but differs in being less efflorescent on exposure to a 

 dry atmosphere. Analyses of specimens from Copper Falls, Lake 

 Superior, have obtained, Silica 55 - 50, alumina 21 19, lime 10'56, water 

 11 '93 = 99*68. The Copper Falls variety alters little on exposure. 

 Reported also from trachyte at Schemnitz, in Hungary, and from Pfitsch 

 in the Tyrol. 



Apophyliite. 



Dimetric. In square octahedrons, prisms, and tables. 

 Cleavage parallel with the base highly perfect. Massive 



and foliated. Color white or grayish ; sometimes with a 

 shade of green, yellow, or red. Lustre of pearly : of the 

 other faces vitreous. Transparent to opaque. IL=4'5-5. 

 G. =2-3-2-4. 



Composition. A silicate of calcium and hydrogen com- 

 bined, with potassium fluoride and water, of the formula 

 (PL £Ca) 3 Si -f |KF + *aq=Silica 52*97, lime 2±-: 2, 

 potash 520, water 15 90, fluorine 2-10 = 100-89. B.B. exfo- 

 liates, colors the name violet (owing to the potash), and 

 fuses very easily to a white enamel. In the closed tube 

 yields water which has an acid reaction. Decomposed by 

 hydrochloric acid with the separation of slimy silica. 



