MINERALOGY OF BLACK LAKE AREA. 
15 
American chrome pit, the crystals observed were in general very much 
smaller. 
CHALCOPYRITE. 
Chalcopyrite is found at many places along the serpentine belt, 
as a primary segregation, and associated especially with the diabase. 
In general, the mineral occurs only in small amount, and this is parti- 
cularly true as far as the Black Lake area is concerned. On many of the 
specimens collected, minute specks of a brass-yellow mineral, almost 
microscopic in size, have been observed ; these are soft and react for copper 
and are no doubt chalcopyrite. 
PYRITE. 
Like the chalcopyrite, this mineral has been observed only as a 
primary constituent of the diabase and gabbro, through which it is 
disseminated as occasional microscopic grains. 
Oxides. 
ANHYDROUS OXIDES. 
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QUARTZ. 
Apart from its occurrence as a constituent of the granite and aplite 
dykes, quartz is entirely absent from the area. A few crystals were 
obtained from a boulder found about 5 miles northwest of Black lake; 
these are associated with apatite, and the occurrence is fully described 
under that mineral on page 81. 
The quartz crystals are perfectly colourless and transparent, and 
they vary in size up to 5 mm. in width and 1^ cm. in length. The 
very small crystals are simple combinations of the prism with the rhombo- 
hedra r(101l) and p (Toil), but many of the larger individuals exhibit 
in addition faces of the right trigonal pyramid s(l 121). A trapezohedron 
is also present on several of the crystals, and in all cases where this face 
was observed the crystals were found to be right handed. 
The prism faces are striated horizontally on all the crystals; the 
rhombohedron is quite smooth and bright on the small crystals, but 
dull and lustreless on the larger ones. The trigonal pyramid is bright 
and free from strise. 
Some doubtful new forms were observed on one of_the ciystals 
measured. The principal forms present were b(1010), r(i011), p(1011), 
s(1121), N-(2132), R*(2l33). The edge rs is replaced by four very 
narrow oscillation faces, which, in their order from r to s, have the 
indices 13-6-19*6 (+ Y 1), 9*5 14-5 (+ I 1), 13-9-229 (+ ¥ 1), 6*5-11*5 
(+ % 1). Of these, the last is a fairly well-defined face, but the others 
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