Grey Granite Research Articles

The old or Grey Granite of the Transvaal and Orange River Colony

Sir,—On May 13 of this year a paper was read in the Geological Society of London by F. W. Penny, B.Sc, F.G.S., “On the Relationship of the Vredefort Granite to the Witwatersrand System” (see Geol. Mag., July, 1914, pp. 332–3), wherein the writer suggests “that the Vredefort Granite, instead of being ‘Archæan’, is of a post-Pretoria – pre-Karroo age, if not contemporaneous with, at least connected with, the same epoch of igneous activity as the ‘Red Granite’ of the Northern Transvaal”.

Some Observations on the Eastern Desert of Egypt; with Considerations bearing upon, the Origin of the British Trias

I. Introduction. D uring the past two years I have on several occasions visited that part of the Eastern Desert of Egypt which borders the Red Sea near its junction with the Gulf of Suez. While there I made observations of desert conditions and phenomena which appeared to me to be of interest to the student of the conditions determining the origin of the Triassic rocks of Britain. A few years ago the late J. Lomas dealt very fully with these conditions, having made some studies of South African and Egyptian deserts, and it is with pleasure that I find myself able to confirm or to supplement several of the conclusions to which he came. II. The Igneous ‘Gravels’ and Pebble-Beds. The western side of the Red Sea is flanked by a wall of hills running generally in lines parallel with the general trend of the coast. They rise abruptly from a level or gently sloping coast-plain, which varies in width from under 1 to over 10 miles. The hills are composed chiefly of igneous rocks: red and grey granites, dark andesites and purple porphyries, with some tracts of gneiss and schist. At the foot of the hills, large mounds of angular débris of the igneous rocks occur, running in tongues from the hills out on to the plain, or forming low foot-hills which run parallel with the main range. The mounds themselves consist of unsorted angular blocks and flakes varying greatly in size, and showing as a rule no signs

Glacial Drift under the Saint Louis Loess

Glacial drift in the vicinity of St. Louis seems to have been described first by Professor A. H. Worthen, in 1866.' In 189o, Professor G. Frederick Wright2 reported glacial drift in the following localities within the city limits: (i) Near Forest Park, on the road to Ferguson, beneath 20 feet of loess was bed of gravel 2 or 3 feet thick, which contained granite and other pebbles two to three inches in diameter, some finely striated; (2) at Hyde Park similar section was seen; (3) in the vicinity of Shaw's Garden. Loess had been removed for brick making, uncovering extensively gravelly stratum which contained many granite pebbles. Striae were found on angular limestone fragments. The elevation was 150 feet above the Mississippi River. H. A. Wheeler, in paper On Glacial Drift in St. Louis, in 1895,3 reported blue glacial clay or till 12 feet thick, at West Pine Boulevard and Taylor Avenue, extending westward to Euclid, underneath io to 15 feet of loess. The diameter of the bowlders is said not to exceed one foot. Among the erratics reported were red and gray granite, diorite, dolerite, and quartz-porphyry. In 1896 James E. Todd4 described bowlder clay in St. Louis. His section may still be seen on Laclede Ave. near Sarah St. The till is 8 feet thick, a reddish brown or waxy red clay, containing granite and other foreign pebbles. The overlying loess is 16 feet thick. Frank Leverett, in his monograph on the Illinois Glacial Lobe,5 reported deposits of glacial derivation underlying the loess for few

The Sedimentary Deposits of Southern Rhodesia

I. Introduction. Southern Rhodesia lies between the Rivers Zambesi and Limpopo where they approach nearest to each other, a distance of 400 miles. Its greatest breadth is from the Victoria Falls on the west to the 33rd degree of longitude on the east, a distance of 450 miles, and it has an area of 192,000 square miles. The major portion of this extent is occupied by grey granite and gneiss, and by the metamorphic schists and slates that contain the numerous quartz-veins extensively worked by an ancient people, and now being again opened up for the extraction of gold and copper. The area over which these rocks occur measures 140,000 square miles, the remaining portion being taken up by sandstones and volcanic rocks. Whatever may have been the original condition of the slates and schists of the gold-belts, igneous or sedimentary, they are now so indurated and cleaved by lateral pressure that their present state only is recognized in this paper, and they are referred to as schists or metamorphic rocks, or when associated with the granites and gneisses, are included in the term Archæan rocks. The slates lie at an almost vertical angle, and the lapse of time and vast amount of erosion that took place before they were covered by the deposition of the sedimentary beds now to be described (which, in striking contrast, lie at low angles or horizontally) give rise to the ‘great unconformity’ of Rhodesian geology. The Archæan rocks of Rhodesia have frequently formed the

The Quarrying of Granite in India

At Bangalore, in Southern India, the quarrying of granite slabs by means of wood fire has been brought to such perfection, that an account of the method may not be out of place. The rock is a grey gneissose granite of very irregular composition through unequal segregation of hornblende and the presence of numerous felspathic veins. But it is otherwise very compact, and forms solid masses uninterrupted by cracks for several hundreds of feet. Only near the surface the rock is found split parallel to the surface. In one quarry there is thus, for instance, a 4 feet thick horizontal layer of rather weathered rock, underneath this another layer of fresh rock 3 feet thick; but below this the rock is entirely fresh, and not split. These layers are probably due to the variations of temperature, daily and seasonal.

Art. XI.—On two Stones with Chinese Inscriptions

In the last number (vol. v. parts ii.–iv.) of the Zapiski of the Oriental Section of the Russian Archæological Society (St. Petersburg, 1891), we find an account of two stones inscribed with Chinese characters, discovered on the Upper Orkhon, near the ruins of Kara Balgassun, among a quantity of other remains, by M. Yadrintsef, during his expedition last summer in North-eastern Mongolia, and forwarded by him to St. Petersburg. Here they were carefully examined by M. E. Koch, who reports that the stones are unfortunately only fragments of a much larger monument, and that it is impossible to say whether they both formed part of the same though they were found in close juxtaposition and their contents would apparently support such a conjecture. Most of the characters are easily legible, being very similar in style to those in present use in China, but owing to the fact of the stones being of grey granite, much weatherworn in places, and the age of the inscriptions (upwards of one thousand years old), there are difficulties in deciphering them. They refer to the period of the T'ang dynasty, or, to be more precise, to the time when the Uighurs were dominant in Northern Mongolia; The characters differ in some instances from those in general use and a few are quite illegible. Where these occur dots are inserted in the text. All the lines want both beginning and end.

Geological observations on Easter Ross, Moy, Craggie and Athole

<i>Easter Ross.</i>—A junction of the Old Red and the Gneiss occurs near the summit of Nigg Hill. A fine bed of Arctic marine shells occurs at Cadboll, at 124 feet above sea-level. <i>Moy and Craggie.</i>—Auriferous sand occurs in almost all the streams of Moy and Strathnairn, such as the burns of Moy, Craggie, Altruadh, Altlugie, and in the gorge of the Nairn below Craggie. Here on one occasion in the summer of 1881 I found about 30 grains of gold by scraping out the <i>débris</i> from the seams of the claystone rocks and by washing it out in an iron basin. Limestone rocks containing cubes of galena occur <i>in situ</i> along both sides of the Nairn below Easter Craggie and Daltullich, and also to the east of Clava. Ironstone seems to be abundant, particularly in Strathnairn, and often occurs in the form of slag resting upon peat-charcoal in the ancient bloomeries of the district at Moy, Bunachton, Aberarder, and Clava. The Moy valley is flanked by high terraces. No detrital barriers can be traced at the 1000 feet level. They exist in the shape of the Kame at 923 feet, across the north end of the valley, and again at 953 feet, across the south end of Loch Moy. <i>Athole.</i>—Craig Ower (1400 feet) forms the central height of the south watershed of the vale of Athole. It is crowned by an ancient circular hill fort about 40 yards in diameter. The rampart is formed of boulders of limestone and gray granite. This granite evidently belongs to the Grampians to the north-east. The most singular feature on Craig Ower is the numerous pot-holes in the limestone rocks on the summit.

Geology of Fearn and Tarbat

1. The normal dip of the Old Red sandstone of Moray to the north-west is prolonged across the peninsula of Tarbat Ness. In Fearn and Lower Tarbat there are many exceptions. The dip at Geanies is to south-west, at Balintore Quarry to north, at Balaldie to north-west (slightly), at Cadboll to north-north-east, at Hilton to south-east. 2. The author describes a large cave at Torrel. The knoll over the cave is crowned with the remains of a circular earthen fort 8 yards diameter. The rampart is similar to that of the old hill forts of the country. The cave and its fort must have formed a strong defensive position. 3. Boulders of large grained red and gray granites, porphyrites, and large masses of gneiss and conglomerate occur profusely all over Easter Ross as well as in Fearn and Tarbat. At Tarbat Ness some of these were formed into small stone circles inclosing earthen mounds or ancient graves. The author thinks these boulders were derived from the West Highlands of Ross. 4. At Cadboll, 124 feet above sea-level, are found marine shells; also above the Old Red quarry at Balintore at 50 feet levels; also at Portmahomack, 84 feet. Fossil shells occur in the Old Red sandstone.

The granite, and the junction of the Old Red Sandstone and gneiss in Lower Strathnairn

The Granite of Ben Beurlaich and Maumsale. —The hills which rise to the east of the farms of Largindour, Auchbain, and Mid-Lairgs, and form the natural boundary in this part between Strathnairn and Strathdearn, are composed of one mass of beautiful gray granite, viz., Ben Beurlaich (1575) and the smaller hill of Maumsale (1250) a little to the north of Ben Beurlaich (see Map No. 84 O.S.). The summits of the two hills form broad platforms of granite, exposed in wide patches all round their slopes for several hundred feet lower down. The granite is also to be seen in situ in the hollow between the two hills. On the Strathnairn side the gneiss is in situ along the common base of both hills, but on the Strathdearn side the granite strikes out across the valley and is seen in situ near the road where it was quarried at one time. The Old Red Sandstone from Faillie to Castletown, Daltullich. —Half way between the bridges of Daviot and Faillie the Old Red Sandstone conglomerate appears on the left bank of the Nairn for about 200 yards, with the gneiss on the right bank. The junction of the Old Red and the gneiss is in the bed of the river. Towards Faillie Bridge the Old Red appears for about 20 yards on the right bank of the Nairn at a place between two very large boulders; the one boulder (gneiss) being in the bed of the river, nearer Faillie Bridge, and the other

1. Chapters on the Mineralogy of Scotland

AbstractIn this chapter Dr Heddle considered the micas occurring in Scotland. These he found to be Muscovite or Muscovy glass, and margarodite—of the white micas; Biotite, lepidomelane, and a new species which he proposes to call Haughtonite, after Professor Haughton of Dublin—of the dark micas. He also finds the species pihlite, hitherto unrecognised in Britain, occurring in quantity in the central districts of Banffshire, and in the west of Aberdeenshire.In connection with the first of these micas, the mode of formation of exfiltration veins, and the metamorphism of gneiss into the grey granite of Aberdeenshire, were considered.

Societies and Academies

Societies and Academies

On the Occurrence of Vermiculite in England

That the discovery of a mineral new to Britain cannot fail to be of interest to geologists, is my apology for bringing the matter before the members of this Society to-day; but my desire is not so much to record the discovery as to obtain the help of those interested in geology in elucidating the geographical distribution of the mineral in question. The district of Furness, in North Lancashire, is rich in glacial debris, and it was during a field-day amongst the Boulder clay, on Walney Island, that the Vermiculite was first found by my friend Mr. C. E. Manby. Walney is a small island separated from Barrow by a narrow channel, fordable in some places at low water, and very probably at one time formed a portion of the mainland. Along the shore, and over the greater portion of the island, there is a mass of glacial debris, in the shape of a heterogeneous assemblage of Granites, Felsites, Quartzites, Slates, &c., &c. Amongst the Granites, the Porphyritic Granite, of Wast-dale, is most common, and when newly dug out of the clay is as fresh, hard, and perfect as if recently detached from the rock; but where exposed to the action of the weather and sea-waves, the boulders are quite soft from decomposition. The Vermiculite is found in both Red and Grey Granite, taking the place of Mica, with Quartz and Felspar; but although I have made very careful examination, I have been unable to trace it in the Shap ...