740 MB. F. ETTTLEY OlS PEELITIC FELSITES, 



39. On Peelittc Pelsites, probably of Archl^aj^ Age, from the 

 Flai^ks of the Heeeeoedshiee Beacon ; and on the possible 

 Oeigi]^ of some Epidosites. By Eeane: Eutley, Esq., E.G.S., 

 Lecturer on Mineralogy in the Eoyal Scliool of Mines. (Eead 

 June 20, 1888.) 



[Plate XVH.] 



In a previous communication to this Society * a rock was described 

 (No. 20) in which faint indications of a perlitic structure were dis- 

 cernible. It occurred on the side of the Herefordshire Beacon, 

 overlooking Castle-Morton Common, and a short distance in rear of 

 the well-known cave. 



The specimens now under consideration were derived from the 

 Eabbit Warren near the above-mentioned locality ; IN'o. 1 from a 

 point about thirty yards above the path, where it touches a small 

 beck which runs between the higher portion of the Beacon and the 

 "Warren ; while No. 2 was procured a little above and to the east of 

 this spot, and about halfway up the steep bank of the Warren. 



The first is a rather deep greenish-grey to brownish-grey rock, 

 which, on a smoothly-cut surface, shows a meshwork of very delicate 

 veins, darker than the material of which the rock is mainly com- 

 posed. 



The second specimen is of paler colour, a yellowish-green or buff 

 tint predominating. 



It was difficult at the time to procure better samples, and both of 

 these must be regarded as in a considerably advanced stage of alte- 

 ration. They were, however, kept^ as they seemed to show faint 

 indications of perlitic structure, and although, in sections cut from 

 them, the structure is somewhat obscure, there is nevertheless 

 sufficient proof that it is present. 



A section taken from specimen No. 1 appears by reflected light, 

 under a low power, to consist of greenish-white to greyish-whito 

 matter, broken by small dark specks and curved lines, which un- 

 mistakably denote perlitic structure, although this is, at first sight, 

 somewhat difficult to recognize, owing to the extensive alteration 

 which the rock has undergone. 



The section is seen to be traversed by a network of delicate fissures 

 filled with quartz. 



Erom this it is evident that the rock has been subjected to great 

 pressure and crushed into a mass of angular fragments, ranging from 

 very small dimensions up to about a quarter of an inch in diameter ; 

 but, beyond the actual gape of the veins, which seldom attain -^ inch 

 in breadth, there has been no appreciable displacement of the frag- 

 ments. 



* " On tlie Eocks of the Malvern Hills," Quart. Joorn. Geol. Soc. vol. xliii. 

 p. 499. 



