MINERALOGY OF BLACK LAKE AREA. 
3 
colours, which render them additionally interesting. The area has 
yielded one new species, which occurs in well defined, though minute, 
crystals; this has been named colerainite and is described on page 66. 
In addition to this several amorphous or very compact substances were 
noted, which present a somewhat unusual appearance, but these have 
been found on examination to be not sufficiently definite in chemical 
composition and other characters to admit of their being listed as new 
mineral species. 
For the sake of completeness a brief outline of the essential features 
of the geology of the area and a description of the principal rocks is given 
at the outset, for which, as well as for the map and much of the infor- 
mation relating to serpentine and chromite, the writers are indebted to 
J. A. Dresser’s “Preliminary Report on the Serpentine and Associated 
Rocks of Southern Quebec." 1 Following this, a section is devoted to a 
discussion of the mode of origin of the several minerals and finally, 
each mineral is described in detail. 
GEOLOGY. 
An extensive study of the geology of the serpentine belt in southern 
Quebec was made by J. A. Dresser during the seasons of 1907 and 1909, 
and the conclusions he reached regarding the structure of the area, and 
the mode of origin of the asbestos and chromite, are set forth in a pre- 
liminary report published in 19 13. 2 Since that time a considerable 
amount of field work has been carried out in the area by Robert Harvie, 
but his investigations being still in progress, no final report has yet 
appeared. The following summary of the general geology of Black 
Lake area is based on Dresser’s report. 
The serpentine belt consists of a series of igneous rocks, for the 
most part of basic composition; areally these appear in a discontinuous 
zone striking from the state of Vermont across the province of Quebec 
with a northeasterly, or east-northeasterly trend. The exact age of 
their intrusion is unknown, and it seems possible that it may not have 
been synchronous everywhere throughout the belt. Over a large part 
of the province these igneous rocks are found intruding Palaeozoic sedi- 
ments of Upper Cambrian and lower Ordovician age; in adjacent areas 
to the south, Silurian and early Devonian strata are not intruded,* 
and northeast of Black Lake and Thetford, in the township of Broughton, 
the time of intrusion seems to have been slightly earlier than in the 
greater part of the belt, though even there it is at least post-L’Islet in 
age and possibly late Cambrian. In general it may be said, therefore, 
1 Geol. Surv., Can., Mem. 22, 1913. 
» Ibid. 
*Geol. Surv., Can., Sum. Kept. 1915, p. 214. 
