294 -P>'o/- Bonney — Eozoon at Cote St. Pierre. 



biotite or biotite-hornblende gneiss, moderately fiiie-grained, over 

 which comes a band of no great thickness, of a whitish qnartzose 

 rock, of which a more minute description will be given below. It 

 is one of the so-called Laurentian quartzites. Above this comes 

 a very considerable thickness of darkish gneiss, rather variable in 

 character. Sometimes it is coarser, sometimes finer ; sometimes 

 there is a fair proportion of quartz, sometimes little ; sometimes 

 hornblende dominates over the biotite, sometimes the rock is 

 distinctly banded, with more and less fel spathic layers.' The 

 highest rock seen was a dark, rather micaceous gneiss, of moderate- 

 sized grain. 



A short interval of covered ground separated the last-named rock 

 from a mass of nearly pure pyroxene I'ock consisting of a coarsely 

 crystalline greyish-buff pyroxene ^ with some interstitial pale- 

 reddish garnet and light-coloured mica (associated), a little calcite, 

 etc. In this rock are veins of an asbestiform mineral which has 

 been worked for " rock cotton," and above this comes the crystal- 

 line limestone. The last nowhere affords a continuous section, but 

 occurs in a number of irregular and separate outcrops on the slope 

 and floor of the valley. As the exact relation of these is not easily 

 determined, it will be better to deal with the principal masses. 



The first is on the western slope of the valley, in immediate 

 sequence with the rocks mentioned above. A number of shallow 

 pits have been opened in a wood, and the limestone can be traced 

 down to the road leading into the "hamlet." In one of these pits 

 the dip was about 70° to a point 10° or 15° S. of E. The rock 

 varies considerably in character. Sometimes it is nearly pure 

 calcite (or dolomite),^ sometimes it contains grains, more or less 

 abundantly, of pyroxene or serpentine, which occur either in fairly 

 marked bands or merely scattered. Pyroxenite (greyish) or serpen- 

 tine (lightish-green) occurs locally in irregular nodular masses or 

 interrupted layers, like chert in a limestone. Well-defined Eozoon 

 is not abundant; indeed, regarding the mass as a whole, it is the 

 exception rather than the rule. This structure commonly forms 

 a kind of band, which is founded upon (if the phrase be permissilde) 

 a layer of green serpentine (resembling that in the well-known 

 Counemara ophicalcite) usually not exceeding half an inch in thick- 

 ness, under which comes a whitish pyroxene, but sometimes the 

 one mineral, sometimes the other, is apparently absent. In the 

 neighbourhood of the "foundation" the layers of calcite and serpentine 

 in the Eozoon are often slightly thicker and less regular than in the 

 outer part. The whole band exhibiting the structure generally 

 varies in thickness from about two to four inches ; it appears to 

 pass, rather rapidly, but not always with a sharp boundary, into an 



' One of my specimens, taken as a sample of about the coarsest type, might be 

 callecl a quartz -diorite ; hornblende is abundant in crystals about a quarter of an 

 inch in length. 



^ The pyroxene is always light -coloured, apparently either malacolite or a closely 

 allied variety, but occasionally it might be tremolite {i.e. a variety of hornblende). 



3 Some of my slices show that a little dolomite is present, but, so far as I can tell, 

 calcite is the dominant mineral. 



