Mr. T. S. Hunt's Examinations of some Felspathic Rocks. 359 



VIII. 



Silica 55-80 



Alumina 2690 



Peroxide of iron .... 1*53 



Lime 901 



Magnesia '27 



Potash -86 



Soda 477 



Loss by ignition .... "45 



99^59 



In Chateau-Richer and its vicinity there are found boulders 

 of a well-defined variety of the felspar rock, which has not yet 

 been met with in place. The base is a coarsely granular felspar 

 of a light reddish-gray colour and vitreous lustre, exhibiting 

 everywhere distinct cleavages, and holding imbedded small bright 

 grains of ilmenite, surrounded with thin films of brownish mica. 

 The imbedded crystals of felspar are numerous, and are often 

 3 or 4 inches in length and breadth by an inch in thick- 

 ness. The faces of perfect cleavage are beautifully striated, and 

 the smaller crystals, which are often slender and well defined, 

 are sometimes curved. Hardness, 6 ; density, 2-680 to 2692 ; 

 lustre, vitreous; colour, pale lavender blue, with pearly opal- 

 escence. Semitransparent, fracture conchoidal. Analysis IX. 

 is a cleavable fragment from a boulder found at Chateau-Richer, 

 and X. and XI. are from a similar and larger mass in the neigh- 

 bouring parish of St. Joachim. 

 IX. 



Silica .... 57-20 



Alumina . . . 26-401 



Peroxide of iron . -40 J 



Lime .... 8-34 



Potash .... -84 



Soda .... 5-83 



Loss by ignition . -65 



The district of Montreal also affords extensive exposures of 

 these same felspar rocks, associated with crystalline limestone, in 

 the counties of Leinster and Tenebonne. In the townships of 

 Rawdon and Chertsey they are often fine-grained and homoge- 

 neous, and constitute an exceedingly tough rock, with an uneven 

 subconchoidal fracture, and a feeble vitreous lustre ; this variety 

 is bluish or grayish-white in colour, somewhat translucent, and 

 exhibits here and there the cleavage of grains of felspar. Great 

 bodies of this rock arc almost free from foreign minerals, while 

 other portions abound in a green granular pyroxene, arranged in 

 thin interrupted parallel layers with ilmenite. These layers 

 of pyroxene are seldom more than 4 or 5 lines in thickness, 



