181o.] in the Physical Sckiices. 45 



7. Prehnite. — Two varieties of prehnite have been analysed bv 

 Gehlen : the first, from Fassutiiale, had a specific gravity of 2*9 17; 

 the specific gravity of the second, from Katschinices, was 2*924. 

 The first variety was composed of 



Silica 42-875 



Alumina 21 '50 



Lime 26-50 



Oxide of iron 3-00 



manganese 0*25 



Magnesia, a trace. 



Volatile matter 4*625 



Soda 0-27 



Loss -98 



100-000 

 The constituents of the second variety were. 



Silica 43-00 



Alumina 23-25 



Lime 26*00 



Oxide of iron 2-00 



manganese 0-25 



Magnesia, a trace. 



Volatile matter 4-00 



Loss 1-5 



100-00 

 Another mineral found in a dolomite rock at Hafnerszell, which 

 from its characters and constituents he considered as a variety of 

 prehnite, was likewise analysed by Gehlen. 



This mineral is amorphous. Its colour is light greenish-grey 

 passing into yellow. It appears foliated, or rather radiated, and 

 exhibits a two-fold cleavage parallel to the faces of a four-sided 

 rectangular prism. Its fracture is splintery; its specific gravity, 

 2-676. ft gives sparks with steel, scratches glass, but is itself 

 scratciied by quartz. It is difficultly frangible. Lustre pearlv, 

 inconsiderable. Translucent. Phosphoresces when heated. Become'*' 

 strongly electric by heat. Its constituents were, 



Silica 54.50 



Alumina 25-25 



Lime 10-05 



Magnesia 3-25 



Oxide of iron 1-00 



■ manganese, a trace. 



Soda 5.91, 



99-99 

 8. Conite.—'n\Q mineral called conite, described by Schumaciier, 



