found in the Neighbourhood of Glasgow. 413 



to B'5 per cent., prevents us from reducing it under the com- 

 mon formula of chabazite. But the formula which it gives is 

 simpler, and may ultimately be found to belong to pure cha- 

 bazite. 



8. Analcime. — This mineral, which Werner distinguished 

 by the name of cubizile, was first noticed by Dolomieu. It 

 occurs rather abundantly in the Kilpatrick hills. In these 

 hills it is white and translucent; but in the Giant's Causeway 

 in Ireland, transparent crystals of it are found. It is crystal- 

 lized in cubes, whose angles are usually replaced by three 

 planes. In most crystals these planes have increased so much 

 in size as to obliterate the primary faces. The crystal is then 

 an imperfect sphere bounded by twenty-four equal trapezoidal 

 planes. This figure is well known to mineralogists by the 

 name of the leucite crystal. 



It is but an imperfect zeolite ; yet it melts before the blow- 

 pipe, though without ebullition ; and like the other zeolites, is 

 soluble in muriatic acid. Its constituents are silica, alumina, 

 soda and water. Atoms. 



Silica... 55-36 27*68 



Alumina 23-00 10*22 2*8 



Soda 14-19 3-55 1 



Water 8-08 7*18 1377 



100-63 

 3 Al S 2 +NSH2 Aq. 

 The translucent and transparent analcimes have the same 

 composition. 



9. Cluthalite. — I have given this name to a mineral which 

 occurs in the Kilpatrick hills near Dumbarton, forming large 

 nodules in the amygdaloid of that district. 



Its colour is flesh-red ; it forms a congeries of imperfect 

 crystals, seemingly rectangular prisms. It is nearly opake, has 

 a vitreous lustre, is harder than calcareous spar, and has a spe- 

 cific gravity of 2" 166. 



Its constitution bears a certain analogy to analcime, the 

 alumina being partly replaced by magnesia, and the soda by 

 peroxide of iron. 



Silica 51*266 ... 9'35 



Alumina 23-560 \ 



Magnesia 1*233 J 



Soda 5-130 1 



Peroxide of iron ... 7*306 J 

 Water 10-558 ... 3*43 



99*048 

 4 (Al + Mg) S 2 + (f N) S 2 + 3 Aq. 



