Prof. T. G. Bonney — North- Western Charnivood Forest. 549 



viridite, often in very minute flakes, but sometimes large enough to 

 be recognized as a chlorite; (2) rather irregularly outlined scales 

 up to about "01 inch in length and "002 inch in thickness, pale green 

 to almost colourless, giving with crossed nicols fairly bright tints 

 and straight extinction, probably a hydrous mica ; (3) many grains 

 or granules, with rather irregular outlines, under -01 inch in 

 diameter, water-clear, and possibly a secondary felspar. In this 

 ground-mass iron oxides, mostly ilmenite, now largely leucoxene, 

 are fairly abundant, in shape rather elongated and irregular. 

 Probably the rock was once a basalt or dolerite. ' Greenstone ' dykes 

 are not very rare in the Forest rocks, sometimes in fairly good 

 preservation, but at others so crushed that I once mistook them for 

 slates. 1 Like those at Stewart's Hay, this basic dyke shows the 

 effects of pressure more conspicuously than the rock in which it is 

 intrusive. 



The Forest Rock quarry has been opened by the road from 

 Leicester to Whitwick in the southern flank of the Spring Hill 

 moorland, some 300 yards west of the Peldar Tor quarry. It is 

 already a large one with a deeper excavation on the western side of 

 the entry. The dominant rock is a porphyroid, with quartzes 2 and 

 felspars about the size of those at Peldar Tor and Sharpley, in 

 a ground-mass which in colour and texture more resembles the 

 latter ; in fact, the specimens remind us now of the one, now of the 

 other. Sometimes, however, the felspars exhibit a roughly parallel 

 arrangement, and the rock then looks more schistose than is usual 

 on Sharpley. This, however, is to a large extent due to a subsequent 

 pressure, which in the part of the pit where it was most conspicuous 

 must have acted roughly at right angles to the direction of fluxion. 

 Both varieties of this porphyroid are associated with a rather compact 

 purplish one, which to the unaided eye resembles those cutting the 

 Peldar rock in the quarries at the Tor and on Bardon Hill. It is 

 distinctly the intruder, sometimes showing a sharp junction and 

 even including fragments, occasionally over a foot across, of the 

 other one, which here and there it has almost digested. 3 Both rocks, 

 but especially the more porphyritic one, contain fragments of the 

 greenish fine-grained speckled rock, so commonly enclosed in the 

 Peldar porphyroid at the other two localities. 



In this pit, however, the compact intrusive rock, which to the 

 unaided eye so closely resembles those at Bardon Hill and Peldar 

 Tor, differs from these under the microscope. It has undergone 

 a greater amount of secondary change than one would have 

 anticipated. The felspars, which are the best preserved constituents, 

 form a plexus of laths, in length ranging about - 01 inch, and 

 indicating by their extinction angles a plagioclase near to oligoclase. 

 The intervening ground-mass consists of an iron oxide, brown or 



1 Quart. Journ. Geol. Soc, vol. xxxiii, pp. 785-6, 1877. The mistake is 

 noticed, id., vol. xlvii, p. 91, 1891. 



2 Locally of a reddish colour. 



3 We find sometimes, within 2 or 3 inches of a junction, solitary grains of 

 quartz and half-destroyed felspars, which can only have been derived from the 

 Peldar porphyroid. 



