On some Veins of Granite in the Carbonaceous Rocks on the North and East of Dartmoor
Authors: Ormerod G. Wareing 
Published: October 2009

The author referred, in the first place, to the ‘Report on the Geology of Cornwall, Devon, and West Somerset,’ where Sir H. De la Beche writes (p. 184), “On the north of Dartmoor we find two elvans in the Carbonaceous series, one on the west of Arscot near South Zeal, and the other running through Lidbridge and Lidleigh Ball, on the south-west of Hatherleigh. Dykes of this kind have not hitherto been detected to the east of Dartmoor.” He then mentioned the following localities on the north and east of Dartmoor, where the Carbonaceous rocks are intersected by granite- or elvan-dykes. Near Meldon (marked in the Ordnance Map as “Elmdon”, to the south-west of Okehampton, granite-veins penetrate the Carbonaceous rocks near the spot where the white granite was worked. On Cocktree Moor, to the south of North Tawton, he was informed that a granite-vein had been found. The Carbonaceous rocks on both sides of the narrow gorge through which the river Teign passes, after leaving the granite near Chagford, are intersected in many places by these veins.

On the northerly or left bank, on the hill-side above the Logan-stone, a short distance below Hunt's Tor, there is a bed of fragments of Carbonaceous rocks that have fallen from above, and granite-veins occasionally occur amongst these portions, showing that a vein probably exists in that locality. A little lower down the stream turns to the south, and shortly turns again eastwardly. The hill-side from near this last turn to some bold cliffs, known as Sharpy Tor, about a quarter of a mile lower down the valley, is seamed with veins of granite. On account of the depth of soil, and the vegetation, they can rarely be traced for more than a few yards,—they do not appear, except in one case, in the cutting for the walk at the top of the hill,—and they have not been noticed on the north side of the hill or at the Drewsteignton Quarries. The veins throw off branches into the adjoining rock, and vary in thickness from a thin filament to a breadth of about 18 feet. In the small veins the granite is very hard and close-grained; in the 18-feet vein it is of a larger grain, and the felspar is often of considerable size: the veins contain portions from the adjoining Carbonaceous beds, sometimes so slightly removed from the original position that it can be traced; in the large veins some of these masses are rounded, as if they had undergone attrition, but some (about a cubic foot in size) still preserve their angularity. This wide vein is very conspicuous, and can be traced for a considerable distance up the hill-side. The strata adjoining the veins are not contorted or thrown violently out of position by the intrusion of the granite; the displacement would probably not be noticed by a general observer, and presents an appearance such as would be caused by a continuous strong pressure.

below Sharpy Tor, granite-veins have not been noticed on the left bank of the river. On the right bank at the most northerly part of Whyddon Park near the gate leading into the Moreton Woods, at the turn in the river below the Logan-stone before mentioned, many scattered blocks of Carbonaceous rocks traversed by granite-veins occur; the rocks are not well exposed, and one granite-vein only has been found
in situ
. The depth of the soil and the vegetation preven the examination of the strata on this bank of the Teign.

To the south of the Teign, two narrow veins of granite, having a direction from N. by E. to S. by W., cross the road from Cranbrook Castle to Fingle Bridge; and a vein of granite, about 19 inches in width, having a direction from N.E. to S.W., in the same vicinity, crosses the road when descending the hill to the west of Cranbrook Farm. The open country to the north of Willistone (about half a mile to the east of Cranbrook Farm) is strewed with blocks of granite and carbonaceous rocks, the latter for the most part much altered and siliceous, and in these scattered rocks veins of granite occasionally occur; the rocks here are rarely exposed in
situ
, and the places from whence these veins are derived have not been discovered; but there seems to be every probability that they are in the immediate neighbourhood. Mr. Ormerod has not examined the junction of the Carbonaceous beds and the granite further to the south than this point.