180 On some Minerals from Lake Superior. 



red colour, from the presence of innumerable spots of sesqui- 

 oxide of iron deposited within or just beneath the surface-layer. 



7. Anthracite. — In the Revised Report (1863) issued by the 

 Geological Survey of Canada, a small amount of anthracitic 

 matter is said to occur in cracks in the chert-beds of the lower 

 division of the upper copper-bearing rocks of Lake Superior 

 (altered strata of Lower Silurian age), as seen in the vicinity of 

 Thunder Bay. A small vein of this kind, nearly vertical in posi- 

 tion and averaging about 5 or 6 inches in width, occurs on the 

 north shore of the bay. It was discovered by Mr. Herrick, a 

 surveyor well known in Canada by his extended explorations in 

 this remote district. A thin layer of colourless quartz lines the 

 walls on each side. This is followed by about half an inch, or 

 rather more, of iron pyrites, possessing a radiated structure, but 

 crystallizing on its inner surface in combinations of the cube 

 and octahedron. To this succeeds another band of white crys- 

 tallized quartz ; and the middle of the vein is filled with black 

 and highly lustrous anthracite. The vein thus offers, though 

 of small size, a fine example of banded or riband structure, 

 showing, in passing from one wall to the other, (1) quartz, (2) 

 iron pyrites, (3) quartz, (4) anthracite, (5) quartz, (6) iron 

 pyrites, and (7) quartz. Here and there a thin coating of 

 anthracitic matter occurs also on the surface of the pyrites, or 

 runs through the latter, dividing it into two or more layers. So 

 far as my observations go, all the large mineral veins of this 

 district exhibit, on the other hand, a brecciated structure, with 

 very subordinate or irregular indications of banding. 



The anthracite from this vein possesses the following charac- 

 ters : — colour, jet-black with high lustre ; streak, greyish black. 

 Very brittle. Fracture, more or less conchoidal. H = 2'25-2*5. 

 Spec. grav. (as determined by a light spec. grav. bottle) = 1'43. 

 Before the blowpipe it cracks slightly and loses its surface-lustre, 

 but exhibits no further change. Heated in a small flask or 

 bulb-tube it gives off a little moisture, but without any accom- 

 panying trace of bituminous matter. In powder, in a thin pla- 

 tinum capsule, it burns completely away, but a long-continued 

 ignition over a Bunsen's burner or double-current lamp is neces- 

 sary to effect this. Carefully selected fragments do not leave a 

 trace of ash. 



Two assays gave the following results : — 



Moisture 2*08 2*23 



Additional loss by ignition in closed vessel 3*56 3*62 



Ash 0-00 000 



Fixed carbon, by difference ..... 94*3G 94*15 



University College, Toronto, Canada West, 

 December 1865. 



