No. 4.J HARRINGTON — CANADIAN MINERALS. 245 



this is not improbable, as some varieties of hornblende are known 

 to contain several per cent, of alkalies. 



Another dyke, occurring- within a few yards of that just de- 

 scribed, is also of much interest. It is dark grey in colour, and, 

 like the last, shows numerous acicular prisms of hornblende pen- 

 etrating the mass in all directions. Here and there macroscopic 

 scales of dark brown mica are seen, and the rock is dotted with 

 numerous spots — occasionally as much as a quarter of an inch 

 across — of a glassy, colourless to white mineral, which, on analysis, 

 proves to be analcite. The specific gravity of the analcite is 

 2.255, and its composition as follows: — 



Silica '. . 53.29 



Alumina 23.33 



Ferric oxide trace. 



Lime 0.64 



Magnesia trace. 



Soda 14.54 



Water 8.47 



100.27 



The mineral was examined for potash, but none found. Before 

 the blow-pipe it fuses easily to a colourless glass. When thin sec- 

 tions of the rock are examined with the microscope the analcite 

 appears very transparent and shows but few inclusions. It is 

 traversed by numerous reticulating cracks, but displays no char- 

 acteristic cleavage. The feldspar is mostly dull, but here and 

 there is sufficiently transparent to show its triclinic character 

 with polarized light. The hornblende and titanic iron appear 

 exactly similar to ^vhat occurs in the ordinary diorites of the 

 locality. No augite has been observed, but one slide shows 

 numerous green crystals, which are evidently pseudomorphs of 

 serpentine after olivine. 



In so far as its constituents are concerned, this rock appears 

 to be somewhat similar to that which Tschermak, many years 

 ago, called teschenlte^ after Teschen in Austria. Tschermak re- 

 garded 'Jie analcite as one of the normal constituents of the rock, 

 and this it may possibly be in the present instance. On the other 

 hand, the general similarity of the other constituents of the rock 

 to those of the ordinary diorites of the vicinity would lead one to 

 infer that the analcite is a secondary mineral, and that the rock 

 is simply an altered diorite. 



The diorites described above traverse not only the Lower 



