OF THE ROCKS OF LAKE SUPERIOR. 257 



" Nepheline Rock" of Lobau, in Saxony. It cannot be distinguished from it in 

 hand specimens, and probably contains either nepheline or eleeolite. It also con- 

 tains a mineral having the characteristic appearances of Olivine. It cuts through 

 all the rocks in this locality. It bears a much greater resemblance to some of the 

 dolerites, as No. 603, for example, which bears N. 30° E., than it does to the 

 greenstones which have the same bearing with itself. If placed among the green- 

 stones, it should be put down as a basaltic variety. 



614. Metamorphosed rock. Has the appearance of a fine breccia; the fragments 

 small and recemented by oxide of iron. The rock appears to have been derived 

 from the beds of the Palisade series, probably the upper part. Colour of the frag- 

 ments, gray ; but the rock has a reddish, mottled appearance, in consequence of the 

 colour of the cementing material. It has a very peculiar, lumpy appearance, as 

 though the sedimentary rock had been broken into innumerable small fragments, 

 but without much displacement. Cleavage planes or planes of lamination are still 

 very obvious. It contains numerous irregular cavities, from half an inch to an inch 

 in diameter, and compressed in a line with the planes of lamination. These cavities 

 are filled with steatitic mineral ; the central portion of a dirty white colour, and an 

 external coating of a greenish-brown colour. Fracture, exceedingly irregular and 

 lumpy. Disturbs the needle very feebly. Belongs to the felspathic bedded rocks. 



615. Bears N. 45° E. Colour, greenish black. Belongs to the basalts, and 

 might be called a basaltic greenstone. Crystalline ; the crystals small and not very 

 obvious. An occasional large crystal of green felspar. Contains numerous aggre- 

 gations of mica in rounded masses, the scales arranged in radii, and proceeding from 

 a black centre. The aggregations are about half an inch in diameter, the black 

 centre about one-eighth of an inch, and then the plates assume a yellow colour, with 

 metallic reflections, bright, and sometimes of a coppery hue. This yellowish part 

 forms a ring around the black centre, about one-eighth of an inch wide, and beyond 

 this the plates become black like the centre, and are lost in the rock. This mica 

 is transparent, inelastic, brittle, sectile, foliated. B. B. it fuses easily in the forceps 

 to a white enamel ; intumesces ; and, in some instances, the enamel is blebby. This 

 rock is probably the same as No. 613. This appears to be the newest dike at this 

 place, and in some parts shows a decidedly columnar structure. This may be seen 

 at the point on the main shore, opposite Encampment Island. Magnetic. 



616. Anorthite rock — highly crystalline. Colour, dark gray. Has much the 

 aspect of quartz. Has all the characteristics of No. 328, differing only in colour. 

 This specimen shows its contact with a basaltic dike, in which immense fragments 

 of it are embedded, and from one of which the specimen was taken. The dike is 

 magnetic, while the anorthite rock is not. 



617. Bears N. 45° E. This is a very fine-grained trappous rock, resembling, a 

 good deal, the fine-grained greenstones, and especially those of a slaty character. 

 It also bears a great likeness to the metamorphosed siliceous shale-beds of " Hat 

 Point," as well as to those of a similar character on Kinechigakwag Creek. It con- 

 tains a great deal of magnetic oxide of iron, in grains and crystals. It is almost 

 homogeneous. The weathered surface is very light gray, nearly whitish, with 

 numerous minute black points of oxide of iron. The felspar is white, and weathers 



33 



