Mr. T. S. Hunt's Examinations of some Felspathic Rocks. 361 



At La-Chute on the Riviere du Nord, there is a felspar rock 

 associated like the others with crystalline limestone, and holding 

 in a greenish granular base a cleavable felspar resembling ande° 

 sine m composition. Its lustre is vitreous, and the face of perfect 

 cleavage, as in all these felspars, is finely striated. Density 2-687 ■ 

 colour, lavender-blue, passing into sapphire-blue; semitrans- 

 parent. Its analysis gave — 



XV 



Sl , 3ica 58-15 



Alumina 26*09 



Peroxide of iron -50 



Lime 



7-78 



Magnesia .jg 



Potash j-2j 



Soda 



Loss by ignition .45 



99-89 

 The bytownite of Thompson appears to be one of these era- 

 nular felspar rocks, and can scarcely be distinguished from some 

 of the varieties just described. In 1850 I examined an authentic 

 specimen of the mineral, and found it to have a hardness of 6-5 

 and a densitv of 2-732 • it cc,™ l™ o«„i„~;~ ' 



i — *".., uuu iwuuu ii, tu iia,ve c 



and a density of 2-732; it gave by analysis,— 



Silica . 

 Alumina . . 

 Peroxide of iron 

 Lime 



Magnesia . 

 Potash . . . 

 Soda . . . 

 Loss by ignition 



47-40 47-30 



30-45 



•89 



14-24 



•87 



•38 



2-82 



2-00 



9905 



I remarked at the time, the undoubted felspathic character of 

 the mineral, which I described as corresponding to the thior- 

 sanite of Genth, and as probably anorthite with an admixture of 

 quartz*. 



The frequent association of ilmenite with these felspars, derives 

 add.tional interest from the fact, that the immense deposits of 

 this ore at Bay St. Paul are accompanied with a lime felspar. 

 nrT™?5 ! d f , man y s ™" er ^sscs, a body of titaniferous iron 

 ore 300 fee long by 90 feet wide, is exposed on the side of a 

 Hill, and a still larger mass is said to occur in the vicinity. The 



* See this Magazine S. 4. vol. i. p. 324. Also Report of the Geological 

 Sarvey of Canadafor 1850-51, p. 38, where analyse XIV. has also appS 



