Vol. 57.] IGNEOUS ROCKS OF THE TORTWORTH INLIER. 2S1 



[b) The Avening-Green and DaniePs Wood Exposures. 



The rocks exposed at Aveuing Green are so much weathered that 

 we had no sections cut. 



The trap exposed in the stream crossing Daniel's Wood is of a 

 rather different type from most of the others. The felspars appear 

 as — (i) minute needles; (ii) laths which are generally shorter 

 and wider than is usually the case in these rouks, and give a 

 maximum extinction-angle of 20° ; and (iii) phenocrysts having 

 a maximum extinction-angle of 44°. Small patches of brightly- 

 polarizing enstatite occur which sometimes show crystal-outlines. 

 (Jther patches of rhombic pyroxene are more or less converted 

 into bastite-pseudomorphs. Augite is also present, both in the 

 groundmass and as phenocrysts. Grains of corroded quartz are met 

 with again here. 



The rock exposed at the end of the field which is almost sur- 

 rounded by Daniel's Wood, is compact and dark brown, and shows 

 in a hand-specimen small felspar-phenocrysts, numerous grains of 

 quartz, and a few araygdules, one of which, reachiag a length of 

 1| centimetres, was filled with chalcedony. Mr. Parsons finds that 

 the silica-percentage is 58*16, and remarks on the fact that it is 

 lower than in the rocks from Charfield Green and Middle Mill (see 

 pp. 279 & 282), in spite of the abundance of quartz-grains. 



In section the rock is seen to be extremely similar to that just 

 described from the stream crossing Daniel's Wood. The minute 

 needles and felspar-laths are identical in the two rocks; but the 

 phenocrysts, which are much rounded, are larger and more numerous 

 in the rock with which we are now concerned than in the Daniel's 

 Wood rock. They are very much altered, and are bordered by a 

 wide band of fresh secondary felspar. Enstatite and augite are 

 both plentiful. The larger crystals of enstatite are converted into 

 bastite-pseudomorphs, and sometimes wrap round the ends of the 

 felspar-laths in an ophitic manner. The augite is the freshest 

 met with in any of the rocks of the district. The included quartz- 

 grains are of the same type as elsewhere in the district, and the 

 chalcedony filling the vesicles is sometimes spherulitic, giving a black 

 cross under crossed nicols. 



(c) The Damery, Mickle-Wood, and Middle- Mill Exposures. 



The rock from Damery Quarry is certainly the one to which 

 most reference has been made by former observers. As described by 

 Mr. Teall in the JBrit. Assoc. Excursion-Guide to Tortworth, 1898, 

 p. 11 :— 



' It is a fine-grained, pnrplish, massive rock traversed by thin veins of 

 calcite. Some of the joint-surfaces are coated with chlorife. Under the 

 microscope the rock is seen to be mainly composed of felspars showing lath- 

 shaped sections. A fibrous bastite-like niiiieral (apparently representing 

 enstatite), carbonates, chlorite, and iron-ores, are also present. The felspars 

 appear to be in part oligoclase, but orthoclase may also be present. The state 

 of preservation of the rock is not such as to admit of precise determination.' 



