Grenville A. J. Cole — Igneous Bodes of Stanner. 223 



In order to see whether the felsites of Stanner could be corre- 

 lated with the clearly acid and more crystalline pegmatite, as 

 common offshoots of some granite mass below, I made the following 

 analysis of a specimen from the central area. The specific gravity, 

 determined from a large specimen by Attwood's balance, is 2*62. 

 Spherulitic Quartz-Felsite, Stanner. Eock. 



Si0 2 ... ... 74-80 



A1 3 3 ... ... 13-89 



Fe 3 03... ... trace 



Cat) ... ... 2-59 



MgO... ... -05 



K 2 ... ... 2-74 



Na 2 0... ... 5-45 



Loss on Ignition -77 



100-29 



The rock belongs, then, fairly to the Acid series, but to the 

 " granitite " rather than the granite group ; similar proportions 

 of the alkalies, implying a fair amount of oligoclase-material, are 

 found even among the rhyolites. 



I have not been fortunate enough to find these white felspathic 

 rocks repeated on Hanter Hill, though the community of other 

 characters in the two hills leads one to suspect that they occur. 



II. The " Diabase " Series. 



The greenstones that compose the bulk of Stanner Eock form 

 various links in the series between the augite-plagioclase rocks 

 and the ordinary hornblende-diorite group. In coarse-grained speci- 

 mens from Hanter Hill, as well as from Stanner, green fibrous 

 crystalline areas occur that by their extinctions may well be altered 

 enstatite. The pale green products that abound, however, are very 

 largely chloritic, and may be considered " tertiary " in origin, when, 

 as is so frequently the case, they are derived from the acicular or the 

 more massive hornblende that is itself developed at the expense of 

 diallage or augite. Olivine was very probably a constituent part 

 of the summit masses of Hanter Hill ; and, following the nomen- 

 clature adopted by Prof. Judd, 1 the rock is there a diallage-gabbro 

 traversed by veins of dolerite, to which the small rounded augites 

 give a marked granulitic structure. The felspars are extensively 

 " schillerized," 2 and even the minuter augites of the dolerites 

 are in the diallage condition, chloritic pseudomorphs resulting from 

 their complete and final alteration. In one gabbro the passage from 

 diallage into hornblende is very beautifully seen. 



But many of the greenstones of Stanner show no signs of former 

 olivine, while chlorite is extensively developed in them from diallage, 

 augite, and green hornblende. In one fine-grained holocrystalline 

 rock, with a specific gravity of 2-86, biotite and augite are closely 

 intergrown (Fig. 3), and form, with plagioclase felspar, the chief 

 original constituents. Titanoferrite and prisms of apatite are also 

 present. The biotite and the augite alike pass into green products, 



1 " Tertiary Gabbros, etc., of Scotland," Q. Journ. Geol. Soc. vol. xlii. p. 62. 



2 Judd, Q. J. G. S. vol. xli. p. 383. 



