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Updated: May 20, 2025
Once across the range we had seen from Mount Bannerman a range of quartzite hills which I named Cummins Range, after the Warden at Hall's Creek and we had reached the watershed of the tributaries of the Margaret and Fitzroy Rivers.
The higher hills west of Seal Lake are capped by a much altered gabbro that has undergone considerable weathering. Between the Nascaupee River and a few miles beyond Bibiquasin Lake the rock is quartzite, considerably weathered and covered by drift.
They resembled a carbon formation sometimes found in quartzite, but were many times more brilliant than anything I had ever seen, excepting precious stones. The hides which covered the granite couch were also unknown to me; they were of an amazing thickness and incredibly soft. We were amusing ourselves with an attempt to pry one of the bits of gold from the wall when we heard a sound behind us.
Sandstone may be converted into quartzite, and shale into ARGILLITE, a compact, massive clay rock. New minerals may also be developed. Where the changes are most profound, rocks may be wholly made over in structure and mineral composition. In contact metamorphism, thin sheets of molten rock produce less effect than thicker ones.
Falls of St. The lower portion is a conglomerate with quartz pebbles. I have seen the Potsdam sandstone on the banks of the St. Lawrence, and on the borders of Lake Champlain, where, as at Keesville, it is a white quartzose fine-grained grit, almost passing into quartzite.
One of many such may be cited in the Star vein at Cherry Creek, Nevada, which, nearly at right angles to their strike, cuts belts of quartzite, limestone, and slate, maintaining its peculiar character of ore and gangue throughout. This and all similar veins have certainly been filled with material brought from a distance, and not derived from the walls.
Sandstone cropped out in deep gullies, and in the bed of the river; it was naturally soft and coarse, but where it rose into hillocks near basalt, it changed into a fine baked sandstone, resembling quartzite, which, when in contact with the igneous rock, looked like burnt bricks.
And because here the snow-fountains lay at a greater height, while the rock, an exceedingly hard quartzite, offered superior resistance to post-glacial agents, the ice-characters are on a larger scale, and are more sharply defined than any we have noticed elsewhere, and it is probably here that the last lingering glacier of the basin was located.
Quartz, dense and milky, also in quartz of nearly every colour and appearance, saccharoidal, crystalline, nay, even in clear glass-like six-sided prismatic crystals, and associated with silver, copper, lead, arsenic, iron as sulphide, oxide, carbonate, and tungstate, antimony, bismuth, nickel, zinc, lead, and other metals in one form or another; in slate, quartzite, mica schist, granite, diorite, porphyry, felsite, calcite, dolomite, common carbonate of iron, siliceous sinter from a hot spring, as at Mount Morgan; as alluvial gold in drifts formed of almost all these materials; and once, perhaps the most curious matrix of all, a small piece of apparently alluvial gold, naturally imbedded in a shaly piece of coal.
The discovery of the true age of these fossiliferous rocks was one of the most important steps made of late years in the progress of British Geology, for it led to the unexpected conclusion that all the Scotch crystalline strata to the eastward, once called primitive, which overlie the limestone and quartzite in question, are referable to some part of the Silurian series.
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