

PEECAEBONIEEEOUS KOCKS OP CHAENWOOD FOEEST. 201 



roughly triangular or quadrangular ; numerous larger felspar frag- 

 ments, both orthoclase and plagioclase, fairly well preserved ; seem- 

 ingly a few lapilli, some showing minute plagioclase crystals ; there 

 are very abundant minute crystalline granules of epidote, besides 

 larger crystals, also viridite in irregular filmy patches. The mate- 

 rials of this rock seem to be pyro clastic, not worn by, though perhaps 

 deposited in, water. 



Forest-Bock-Inn Quarry (p. 773). — Ground-mass similar to, but 

 more uniform than last; little or no viridite; not much epidote, 

 but a good many minute grains of some ferruginous mineral. So 

 far as can be inferred from the form of the few larger felspar frag- 

 ments, the materials of this rocli are not obviously water-worn. 



Slate from N.E. corner of Br adg ate- House Woods (p. 787). — One 

 of the finer little-cleaved pale-green slates ; specimen collected about 

 four feet from the syenite ; ground-mass similar to, but yet finer 

 and more altered than, the last ; the more earthy part often in fine 

 clotted granules ; fragmental felspar crystals in bands, many of them 

 almost wholly replaced by secondary microliths, bright- coloured 

 with crossed Mcols ; indications of minute lapilli, but less distinct 

 than in the Ulverscroft specimen. Origin probably similar to that 

 of the last rock. 



Indurated Slate from south end of High Towers (p. 773). — A com- 

 pact flinty rock of greenish-grey colour, with spots and streaks of a 

 dark ferruginous mineral ; in large fragments in an ashy breccia. 

 The ground-mass is very finely granulated and rather earthy-looking ; 

 in it are irregular grains of felspar, seemingly fragments, in tolerably 

 distinct bands. Origin probably as before. 



Ashy Slate near Steward? s-Hay Spring (p. 786). — A much softer- 

 looking and less flinty rock than the last ; syenite is intrusive in it. 

 One specimen has been examined from near the northern junction 

 with that rock and two from near the southern, one of these ex- 

 hibiting actual contact ; the ground-mass is finely granular, tinged 

 slightly with viridite, with many opaque granules, and numerous 

 felspar crystals of irregular shape and slightly banded arrangement ; 

 many of the larger granules resemble decomposing ilmenite; the 

 form of the felspar crystals generally suggests plagioclase, but this 

 has been replaced by an aggregate of rather fibrous microliths, 

 bright-coloured with crossed Mcols. The longer diameters of the 

 crystals in the junction specimen are roughly parallel and inclined 

 to the bands; they are parallel to the surface; there is a little 

 quartz, probably secondary ; doubtful indications of included lapilli ; 

 the condition of the felspar crystals makes it very difficult to decide 

 whether they are fragmental or of secondary formation ; the ground- 

 mass of the first-named specimen is the most highly altered, and it 

 contains some ill-defined green crystals, possibly altered hornblende. 



(3) Coarser Fragmental Roclcs. — These rocks, though the size and 

 nature of the included fragments vary considerably, may be thus 

 generally described. In a ground-mass, consisting apparently of 

 comminuted felspar more or less altered, and often streaky with 

 a chloritoid mineral, are a number of larger angular fragments of 



Q. J. G. S. No. 134. p 



