Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/307

From Wikisource
Jump to navigation Jump to search
This page has been proofread, but needs to be validated.

the strata are very highly inclined, and dip to the east. In the spaces that intervene between large masses of the granite, there is a rock composed of hornblende and mica, with somewhat of a slaty structure and a loose friable texture. It is intersected by veins, which are sometimes very slender, and in that case they consist of red felspar ; but when the same vein becomes wider, it is found to contain the usual component parts of granite. These veins are disseminated irregularly through the mass, the line of separation is very distinct, and there is no mutual penetration of the two rocks.

§ 26. On the south-east side of the North-hill, and at the entrance of the valley above Great Malvern, which separates that hill from the Worcestershire Beacon, there is an aggregate rock consisting of small angular and rounded fragments of quartz and felspar, cemented by a ferruginous earthy base; the whole in a decomposing state. It occurs in the lower part of the hill, and is probably produced from the disintegration of a granite, the mica of which has been chiefly decomposed and has afforded the cement. Above this aggregate rock, the hill consists almost entirely of granite, in which the materials are in some places so disposed as to give the rock somewhat the appearance of gneiss. It is fresher; than most of the rocks in these hills, that is to say, it is less disposed to break into irregular fragments with decomposed surfaces. It sometimes contains veins of epidote, and in one instance I found in it a slender vein of calcareous spar. Subordinate portions of a mixture of hornblende and felspar occasionally occur in it, and sometimes the hornblende, felspar, quartz and mica are combined in equal proportions, forming a uniform mass. In this part of the hill, I also met with a fine-grained rock, consisting of quartz, felspar, mica and granular epidote, traversed by a narrow vein of granite.

§ 27. The upper part of the Worcestershire Beacon is composed