IGNEOUS EOCKS OF SOUTH-EAST COENWALL. 25 



Of the Dolerites the most interesting section is supplied by 

 Treluggan. It is a dark heavy dull-green crystalline rock, with 

 crystals very distinct and sparkling. The characters of the con- 

 stituent minerals are uncommonly well preserved. They include 

 plagioclase-felspar, hornblende, augite, viridite, chlorite, magne- 

 tite, apatite, and mica. The N otter rock is a dark grey, and 

 contains granular augite, hornblende, plagioclase-felspar, 

 viridite, and ilmenite. Burraton Combe rock is greenish-grey 

 and compact ; and has a much altered grey f el spathic base, 

 with altered ilmenite, apatite, and a little viridite. The most 

 crystalline variety of the Wearde stone is very dark-green, and 

 contains plagioclase-felspar, calcite, quartz, brown mica, horn- 

 blende, viridite, magnetite, and epidote.* The Ernesettle rock 

 most nearly resembles this in composition, though the most 

 typical varieties are a mottled grey — light felspar contrasting 

 with dark hornblende and augite. There are in addition mica, 

 ilmenite, and viridite — augite much altered. 



The Caw sand Triassic Trap is mostly red, occasionally veined 

 and spotted with white. It is slightly vesicular, contains por- 

 phyritic felspars and has two varieties — one earthy, the other 

 compact and semi-vitreous. Mica is evident to the naked eye 

 in some quantity, but under the microscope it is seen to be much 

 more abundant, though it does not compare in this respect 

 with the well-defined Triassic mica-trap of Killerton near 

 Exeter. From the central mass of this trap veins are sent a con- 

 siderable distance, traversing the adjacent slates as far as 

 Millbrook and Whitsand Bay. This rock evidently marks the 

 last epoch of volcanic activity in the West ; and it is associated 

 with considerable disturbance of the Devonian strata adjacent.f 



The latest authority to examine the Clicker Tor rock is Mr. 

 J. H. Teall, who figures and describes it in his fine work on 

 British Petrography. He classes it as a Picrite, and as having 

 been originally an ophitic dolerite or diabase, in which oliviue 



*0n these dolerites see also Mr. Phillips's paper, Quar. Jour. Geo. Soc, Vol. 

 XXXIV., pp. 471—496. 



f Pebbles of a highly scoriaceous lava occur on the beach at Talland, and 

 apparently come from the bed of the Channel. They may be Triassic, but they 

 are quite distinct from the Cawsand trap. 



