258 DESCRIPTIVE CATALOGUE 
more slowly than the other ingredients. Its composition is best seen on weathered 
surfaces. See No. 291. 
618. Bears N. and 8. Very fine granular, apparently homogeneous. Colour, 
purplish gray. Fracture, quite even; disposed to be conchoidal. Very compact. 
May be compared with Nos. 400, 401,419, and 427. Itisa bedded rock, at several 
points, and is, in all probability, a metamorphosed rock; and if so, belongs to the 
fine-grained siliceous slates. There is no appearance of crystallization about it. On 
the other hand, it seems to cross Kanokikopag River, in the form of a dike, and 
does bear some resemblance to the narrow N. and S. dikes of other localities. Mag- 
netic. It is very heavy, and my opinion is, on the whole, that it is most like the 
trap, in general aspect, but like the sedimentary rocks in structure. It breaks into 
rhomboidal prisms. 
619. Metamorphosed siliceo-argillaceous slate. Colour, brick-red, with occasional 
small spots of a deeper brownish red, due to segregations of oxide of iron. Very 
compact. Has a very even fracture. Resembles some of the highly-altered 
quartzites. Jointed; some of the joints lined with highly-crystalline quartz. For 
a short distance on each side of the joints, the rock is discoloured, being of a light 
yellowish red. These beds contain large rounded pebbles of a greenish-coloured 
siliceous shale, very much like the green shales of St. Louis River; and around 
these pebbles is a ring of lighter colour than the body of the rock, like that which 
is next the joints and incrustations of vitreous quartz. This rock resembles closely 
No. 599, and may be compared with No. 635, and also with No. 621 and No. 596. 
620. This rock is like No. 609, No. 188, and No. 359. It belongs to the volcanic 
grit-beds. Colour, purplish gray. Very fine granular; numerous grains and scales 
of the soft magnesian mineral (thalite). Fracture, nodular; irregular. Is allied to 
the basaltic rocks, in so much as the principal materials were derived from them 
either during or immediately after the eruption of basalt. Magnetic. 
621. Fragments of No. 620, in a N. and S. dike, below the mouth of Kanokiko- 
pag River. It differs from No. 620 only in being rather more indurated, of a darker 
colour, and in the development of small segregations of red felspar, and of small 
crystalline lumps of quartz, as are shown in the Great Palisade rock at some places, 
giving it a porphyritic appearance. This specimen contains patches of a lighter 
colour (reddish gray), which show neither felspar nor quartz segregations, and some 
of which appear to have been pebbles derived from older beds of a similar rock. 
The same is the case with No. 620. Magnetic. 
622. Bears, apparently, E. of N. Scent. This rock is composed of lumps of 
quartz, flesh-coloured felspar, and hornblende, the last ingredient being black. The 
felspar, which is rather light-coloured, looks a good deal like that of No. 328. The 
rock is coarse and not very compact, and on weathered surfaces has a singularly 
mottled appearance, caused by the black felspar being disseminated in somewhat 
prominent aggregations through the red felspar base. The rock is jointed, both 
horizontally and vertically, the vertical joints forming angles of 62° and 70° with 
the horizontal ones. In constitution, this rock is a syenite, but is almost certainly 
a metamorphosed rock. The minerals which compose it seem to be in irregular 
