1850.] DAWSON METAMORPHIC ROCKS OF NOVA SCOTIA. 363 



oxide of iron and quartzose sand occurring in the Silurian system, 

 and containing marine shells already mentioned. Others are veins 

 of brown haematite, apparently confined to the lower carboniferous 

 beds, near their junction with the Silurian system. 



In the promontories of metamorphic and igneous rocks, extending 

 toward Cape St. George and Cape Porcupine, veins similar to those 

 already described occur in many places. In the former, at Malig- 

 nant Cove and other places in that vicinity, specular iron ore occurs 

 in slender veins, whose walls are sometimes lined with crystals of 

 epidote. In the latter, near the Lochaber Lake, a mineral district of 

 somewhat interesting character has been discovered. At this place 

 the prevailing rocks are olive, black, and grey slates, and grey quartzite, 

 with dykes of greenstone and clay stone. The general strikes of the 

 beds are S. 70° W. to S. 20° W. magnetic ; and the directions of the 

 bedding and slaty structure correspond. The slates are often very 

 fine-grained and soft, with glistening surfaces, and highly perfect 

 slaty structure. In the slate and quartzite there are innumerable 

 small veins of white quartz and ankerite, with micaceous specular 

 iron and occasionally iron and copper pyrites. The general direction 

 of these veins corresponds with that of the containing beds, though 

 they are often seen to pass from one plane of beddmg or cleavage to 

 another. On the south side of Poison's Lake, two miles eastward of 

 the Lochaber Lake, a large vein of iron and copper ore appears to 

 exist. The slate is here decomposed to a great depth, and among 

 its debris are numerous large fragments of ore marking the outcrop 

 of the vein. Some of these fragments are from three to five feet in 

 diameter. They consist of red ochrey iron ore, with many and often 

 large strings and bunches of copper- and iron-pyrites. No specular 

 iron ore has yet been found in this vein, but there are small quantities 

 of greyish crystalline carbonate of iron, which ma}^ be observed to 

 pass gradually into the red ochrey ore, the latter retaining, often in 

 great perfection, the rhombohedral crystallization of the carbonate of 

 iron. In this we have probably evidence of a change similar to that 

 already supposed to have produced the red ore of the Cobequid hills. 

 Where the carbonate of iron is exposed to the weather, it is occa- 

 sionally seen to be changed into yellow and brown hydrous peroxide 

 of iron. 



The pyrites found in this deposit contains from 4 to 17 per cent, 

 of copper. The most common variety has 10*8 per cent. It is 

 scattered through the red ore in the most irregular manner ; but in 

 general the boundary between the two minerals is marked by a thin 

 crust of hydrous peroxide of iron, perhaps resulting from the decom- 

 position of the surface of the pyrites by water percolating the porous 

 red ore. The larger masses of pyrites occasionally include fragments 

 or crystals of ankerite and carbonate of iron. I confess that the oc- 

 currence of minerals so easily altered by heat, as copper and iron 

 pyrites, in association with red ore, is adverse to the view of the 

 origin of that mineral given above ; unless we can suppose the py- 

 rites to have been introduced subsequently to the production of the 

 red ore. 



VOL. VI. PART I. 2d 



