This view of its origin is now known not to be applicable to the Archean as a whole, since this system contains some metamorphosed sedimentary rocks.
The most certain representatives of the Archean are the gneiss and schists of the Dove river and the upper Forth, and the hornblende-schists, which are exposed in the river valleys on the margins of the central plateau.
By far the greater part of Portugal is occupied by ancient rocks of Archean and Palaeozoic age, and by eruptive masses which probably belong to various periods.
The higher elevations are mostly either Archean or Paleozoic formations projecting above Tertiary deposits.
Above the Archean gneiss lies a series of red and chocolate-coloured sandstone (Torridon sandstone), which form a number of detached areas from Cape Wrath down the seaboard of the shires of Sutherland and Ross and Cromarty, across Skye, and as far as the island of Rum.
Within the Archean protaxis they are of the most varied shapes, since they represent merely portions of the irregular surface inundated by some morainic dam at the lowest point.
Georgian Bay and the northern part of Lake Huron with the whole northern margin of Lake Superior bathe the foot of the Laurentian plateau, which rises directly from these lakes; so that the older fertile lands of the country with their numerous cities and largely-developed manufactures are cut off by an elevated, rocky and mostly forest-covered tract of the Archean from the newer and far more extensive farm lands of the west.
South and east of the Palaeozoic plateau is an extensive area consisting chiefly of Archean rocks, and including the greater part of Mongolia north of the Tian-shan.
Australia is essentially the fragment of a great plateau land of Archean rocks.
The oldest rocks in New South Wales are referrable to the Archean system, and consist of gneisses and schists, including the glaucophane-schists in the New England tableland, and hornblendeschists of Berthong.