Examined more closely these are found to be vast accumulations of blocks of quartzite, irregular in form, but having a tendency to a rude diamond shape, from 2 to 20 ft.
In length, and half as much in width, and of a thickness corresponding with that of the quartzite ridges on the hills above.
Another out of many theories 1 is that the hard beds of quartzite are denuded by the disintegration of the sof ter layers.
(3) The " banket " formation, which characterizes the goldfields of South Africa, consists of a quartzite conglomerate throughout which gold is very finely disseminated.
There are several series of parallel beds, interstratified with quartzite and schist, the most important being the "main reef" series.
In Ankole and Koki rocks consisting of granular quartzite, schistose sandstone, red and brown sandstone, and shales with cleaved killas rest on the Archean platform and possibly represent the Lower Witwatersrand beds of the Transvaal.
In Murua (Woodlark I.) are quarries of the banded quartzite from which the best stone adzes found throughout south-east New Guinea are made.
The commoner sorts of rock in the several Huronian systems are quartzite and slate (ranging from shale to schist); bi~t limestone is not wanting, and igneous rocks, both intrusive and extrtisive, some metamorphic and some not, abound.
Tuscarora quartzite 30 300
Sawatch quartzite 50 350 ft.
Nephin Beg, Nephin and Croagh Patrick are typical quartzite summits, the last named belonging possibly to a Silurian horizon but rising from a metamorphosed area on the south side of Clew Bay.
The oldest rocks are gneiss, schist and quartzite, the schist often containing gold.
In thickness, and contain pebbles of quartzite, jasper, sandstone, slate, &c. The mines fall into five groups situated on the eastern side of the Deccan plateau about the following places (beginning from the south), the first three being in Madras.
The mountains consist here of an ancient laminated micaceous quartzite, which is in parts a flexible sandstone known as itacolumite, and in parts a conglomerate; it is interbedded with clay-slate, mica-schist, hornblende-schist and haematite-schist, and intersected by veins of quartz.
This series is overlain unconformably by a younger quartzite of similar character, and itself rests upon the crystalline schists.
A hard and fine-grained quartzite sandstone was quarried at Jebel Ahmar behind Heliopolis, and basalt was found thence along the eastern edge of the Delta to near the Wadi Tumilat.
The quartzite work from Jebel Ahmar near Cairo stands next, as often very fine design is found in this hard material.
24), but more usually grinders blocks of quartzite sandstone (26-34), and occasionally Df diorite (Q.
The Paps of Jura, for instance, rise out of a long belt of quartzite which stretches through the islands of Islay, Jura and Scarba.
Archean gneiss, Cambrian sandstone, Silurian quartzite, limestone and schist, Jurassic sandstone and limestone, Cretaceous sandstone, and Tertiary basalts, gabbros, and granitic rocks all enter into the composition of the islands.
On the, other hand, there occur bands of conglomerate, pebbly grit, quartzite, graphitic shale and limestone in a certain ordered sequence and over a wide area.
In the north-western Highlands masses of white quartzite, resting unconformably in Torridonian sandstone, run from Loch Eriboll to Skye, forming in places great conical hills and some L J Recent & Pleistocene F l Cretaceous Jurassic Trias Granite & Acid Intrusive Rocks' Permian Coal Measures, Carboniferous Millstone Grit Series Lower Carboniferous Old Red Sandstone & Devonian Silurian Ordovician Cambrian Scale, z:4,600.000 English Miles o xxxx xzxx xxxx Metamorphic Group Volcanic Rocks ® Basic Intrusive Rocks 'I +++ +++ ob.o times capping isolated mountains of red Torridon sandstone.
In descending order they embrace the following subdivisions, whose thickness in the district of Durness is estimated at about 2000 ft.: (e) limestones, dolomites and cherts, with numerous organic remains; (d) grit and quartzite, with Saltarella and Olenellus (Serpulite Grit); (c) calcareous shales and dolomites, with many annelid casts and sometimes Olenellus (Fucoid Beds); (b) Upper Quartzite, often crowded with annelid pipes (Pipe Rock Quartzite); (a) Lower Quartzite - their original upper limit can nowhere be seen, for they have been overridden by the Eastern Schists in those gigantic underground disturbances already referred to, by which these rocks, the Archean gneiss and Torridonian sandstone, were crumpled, inverted, dislocated and thrust over each other.
The Cambrian system - including the Upper (Durness-Eriboll Limestone) and the Lower (Serpulite grit, Fucoid Beds, Quartzite) - forms a narrow band which can be traced for too m.
The mining product next in value to coal in 1908 was copper, taken chiefly in Carbon county in a zone of brecciated quartzite underlying schist, the original ore being chalcopyrite, with possibly some pyrite, a secondary enrichment, which has produced important bodies of chalcocite in the upper workings, but these are replaced by chalcopyrite at greater depth.
In the lower series are, in descending order, the "Serpulite grits" or "Salterclla beds," the "Fucoid beds" and the "Eriboll quartzite," which is divided into an upper "Pipe rock" and lower "Basal quartzite."
The Cambrian rocks of Ireland, a great series of purple and green shales, slates and grits with beds of quartzite, have not yet yielded sufficient fossil evidence to permit of a correlation with the Welsh rocks, and possibly some parts of the series may be transferred in the future to the overlying Ordovician.
The rock is a very compact and fine-grained mixture of felspar, quartz and mica, often graduating to mica schist, quartzite and gneiss.
The geological core of the system consists of primitive argillaceous schists, capped by quartzite and broken through in places by basalt.
Quartz being a mineral very resistant to weathering agencies, it forms the bulk of sands and sandstones; and when the sand grains are cemented together by a later deposit of secondary quartz a rock known as quartzite results.