262 



DESCRIPTIVE CATALOGUE 



635. Metamorphosed siliceo-argillaceous shales — colour, brick red. Fine granu- 

 lar; laminated; structure, compact. Fracture, generally smooth and even, and 

 disposed in some of the beds to be conchoidal. In other beds, the fracture is some- 

 what rough, and shows numerous segregations, darker and apparently harder than 

 the body of the rock. These beds belong to the same shales as Nos. 596, 599, 619, 

 and 621. All these last, however, are metamorphosed in a higher degree than this 

 rock. 



636. Bears E. 10° N. Very fine granular; homogeneous. Colour, gray; with 

 a few minute points of the soft olive-green mineral. Fracture, conchoidal, smooth. 

 Joints and weathered surfaces black and brownish black. This rock is analogous 

 in structure to Nos. 612, 618, and 624. It differs from No. 645 in being somewhat 

 less crystalline in appearance, and in being of a lighter gray colour. It may be set 

 down as a very fine-grained greenstone. Magnetic. 



637. Bears E. 10° N. This rock is the same as Nos. 629 and 633. At the 

 point of the bay where this specimen was taken, it is intercalated with a breccia 

 and soft material containing much zeolitic mineral. It may also be compared with 

 No. 632. From the association of this rock with beds of breccia at this place, I am 

 inclined to class it with No. 188, which belongs to the volcanic grits. The different 

 bearing it has at different points, is also evidence in favour of the opinion that it is 

 a volcanic sedimentary rock, deposited during the basaltic period, and subsequently 

 altered by intrusive dikes of trap. Its close association with the metamorphosed 

 shale-beds also gives weight to this opinion, as similar bedded rocks at other points 

 on the Lake shore, and in the interior, are associated with the shaly and conglome- 

 rate beds, and with the breccias. See Nos. 629 and 633 for descriptions of this 

 rock. Does not disturb the needle. 



638. Bears N. 45° E. This rock may, in one sense, be called a porphyry, as it 

 contains numerous crystals of felspar and hornblende, embedded in a paste. The 

 paste is granular, and made up of rounded grains, while the crystals of the two 

 minerals named are fragmentary. Colour, brownish red ; has an exceedingly rough, 

 scabby-like fracture, looking like that of some of the baked clays; cross fractures 

 without any definite direction, and jagged. The rock is irregularly laminated, and, 

 when struck with the hammer, separates into very uneven plates of irregular thick- 

 ness, the surface being unequal and lumpy. The body of the rock is fine-grained. 

 „It belongs to the shale-beds, and may be compared with Nos. 54, 75, 100, 107, 110, 

 140, and other specimens of the shale-beds from various localities. In general 

 structure, it resembles most nearly Nos. 107 and 140. Magnetic. Weathered sur- 

 face, irregular, but smooth, of a lighter red than the interior of the rock, and 

 relieves beautifully the white crystals of felspar which are disseminated through it. 

 This rock is traversed by at least two systems of dikes, and, probably, three. 



639. Bears N. 10° E. Structure, somewhat granular, with numerous minute 

 crystalline points. Colour, very dark purplish gray, with numerous dark, olive- 

 green spots made by the magnesian mineral. In general appearance, it much 

 resembles the metamorphosed shales referred to when speaking of No. 638. It is, 

 however, more crystalline in its structure, and is, probably, a trap. It is compact, 

 and weathers with a tolerably even blackish surface. 



