On SoMe Dykes Containing Huronite. 43 



and is a noticeable and interesting feature in connection with the rock. 



Additional evidence of pressure is furnished by the frequent distortion 



and even dislocation of both the plagioclase and augite individuals. 



8. Locality. About 4 miles N.YV. Pogamasing Station, main line, 

 Canadian Pacific Railway, District of Algoma, Ont. 



The specimen was obtained from a dyke, cutting the granitoid 

 gneisses of the Laurentian. The phenocrysts of " Huronite " have 

 generally a rude, rounded outline, the largest of which are about two 

 inches in diameter. Many of the smaller ones have irregular or jagged 

 outline, and occasional individuals exhibit some of the sharp faces of 

 the original crystal. The mineral is of the usual light, yellowish-green 

 colour, shows the glistening surfaces of the indistinct cleavage and occa- 

 sional faint-strire. It is sub-translucent, has a waxy lustre, and a some- 

 what " soapy " feel. According to Dr. Harrington* " the hardness is 5. 1 , 



*Trans. Royal Soc. Canada, Sec. Ill, 1886, p. 82. 

 or a little over, fusibility about 5, and specific gravity 2-814." An analysis 

 of some of the material composing these phenocrysts was made by Mr. 

 N. N. Evans, of McGill University, for Dr. Harrington, with the follow- 

 ing results : 



Silica 47' 07 



Alumina 32 49 



Ferric Oxide 097 



Lime 13 30 



Magnesia 022 



Potash 2 88 



Soda 203 



Loss on ignition 272 



roi68 



The matrix in which these crystals are developed is a fine-grained 

 dark ^reen diabase, with abundantly disseminated particles of iron 

 pyrites. 



Uuder the microscope the " Huronite " is seen to consist of an 

 aggregate of epidote, zoisite, sericite and chlorite, but in the larger 

 crystals especially, considerable areas of unaltered plagioclase exist 

 which are quite fresh and glassy, and exhibit the twinning lamellae 

 quite distinctly. The smaller phenocrysts, however, a^e altogether 



