244: DK. J. W. GREGORY ON THE WALDENSIAN [May 1 894, 



The talcose gneiss macroscopically resembles that in contact with 

 the epidiorite in the Vonzo Valley, and subsequently described from 

 Mustione and elsewhere in the Eastern Cottians. It appears to be 

 a gneiss which has absorbed much basic matter from the schists ; 

 while the fact that the garnet-rock above it is crushed and decom- 

 posed is also a result of the contact-metamorphism. 



On the opposite side of the Yallone Verso similar amphibolite- 

 schists can be seen, on the edge of the platform on which stand the 

 hamlets of Casa Girot and Casa Ortiero. Below them occurs a bed 

 of quartzite which strikes towards the gneiss. The latter is well 

 shown in a few small quarries ; the uppermost of these is imme- 

 diately below the quartzite, here altered to a quartz-schist. The 

 gneiss is fine-grained, and in this condition it can be traced up to 

 within 5 metres of the quartzite. In a second quarry, a little 

 below the first, the gneiss is coarser and typically augen, characters 

 which become more prominent as it is followed farther down the 

 hillside. 



The schists and the quartzite here dip 23° south-east with 

 a strike of 32° south of west (magn.), whereas in the lower quarry 

 and in numerous exposures farther down the cliff the foliation of 

 the gneiss has a strike of 10° south of west (magn.). The gneiss 

 below the quartz-schists contains none of the ' talcose ' (or chloritic) 

 material which occurs in it when in contact with the ' pietre verdi.' 



The general conclusion to be drawn from these facts seems to be 

 that the gneiss is here intrusive, as shown by the contact-meta- 

 morphism in the ' pietre-verdi ' series, and the alteration of quartzites 

 into quartz-schists ; and also by the transgressive junction of the 

 gneiss from its contact with the ' pietre verdi ' to the quartzite. 



The actual junction could not be clearly traced, as the hill-slope 

 is here covered with brushwood, but in the absence of any evidence 

 of a fault the strikes certainly favour an intrusive junction. On 

 the north side of Chialamberto I had hoped for clearer evidence of 

 this nature ; but I failed to find the 'terreni cristallini superiori' 

 that Gastaldi figures on either side of the band of ' serpentino, 

 eufotide, ecc' which his map shows in contact with the gneiss on 

 the north-east of Chialamberto. Nevertheless, there is some evi- 

 dence of a transgressive junction along the course of the stream at 

 the base of Monte Bellavarda, opposite Madonna di Ciavinis. The 

 foliation, as measured by Mr. Davies, runs 13° north of west, and 

 along a line at an angle of about 75° with this (i. e. 62° south of west) 

 a definite succession of the beds can be recognized ; this includes 

 ordinary amphibolite-schists, amphibolite with felspar-grains and 

 nodules, and talcose amphibolite-schist. In this series, moreover, 

 occur some masses of altered serpentine, the field-relations of which 

 resemble that common to the peridotites of the Cottians. The rock 

 consists of fairly large crystals of brown bastite, with very well- 

 marked schillerization ; the outlines are irregular and surrounded 

 by an altered structureless zone, which still maintains its optical 

 continuity with the central nucleus. These crystals are enclosed in 

 a light-green serpentinous mass, crowded with needles and radial 



