MINERALOGY OF BLACK LAKE AREA. 
29 
provided the chromium, while the magnesium was derived from the ser- 
pentine. 
Occurrence at Megantic Mine. 
In general appearance, and mode of occurrence, the stichtite at the 
old Megantic mine is remarkably similar to that from Tasmania. More- 
over, the mineral so closely resembles, in its colour, the lilac vesuvianite 
occurring at the Montreal chrome pit, that it was not at first distin- 
guished from the latter. The material has not been analysed, but an 
examination of the general chemical behaviour, as well as of the physical 
and optical characters, proves it to be stichtite. In making the indenti- 
fication, the several characters examined have been checked by direct 
comparison with those exhibited by a specimen received by the Museum 
of the Geological Survey from Mr. W. H. Twelvetrees, government 
geologist of Tasmania. 
The stichtite apparently occurs very sparingly, and only a few 
specimens were collected. In these the mineral appears as small patches, 
and also in the form of narrow veinlets, within the precious serpentine. 
The colour, on freshly broken surfaces, is deep lilac, but it weathers to 
a much paler shade. When examined with a lens, or, in some specimens, 
even by the unaided eye, the mineral is seen to be minutely crystalline, 
light being reflected from numerous very small faces, which are per- 
fectly flat and have a vitreous to oily lustre. These facets no doubt 
represent the basal cleavage referred to in the description of stichtite, 
and no fragment has been isolated showing cleavage in more than one 
direction. The mineral is easily scratched by a pin, and the hardness 
is probably below 2. The specific gravity, by immersion in methylene 
iodide, was determined as 2*166 and 2*185 on two fragments; it is very 
possible that the true value is somewhat lower than 2*166, since it is 
difficult to obtain fragments of the mineral entirely free from serpentine. 
When fragments are crushed in oil and examined under the micro- 
scope, they are found to be made up of minute thin blades or fibres, 
some forming a network, and others arranged nearly parallel. The 
colour is very pale lilac, and there is no perceptible pleochroism. The 
fibres invariably have parallel extinction, and the birefringence is fairly 
strong. Compensation takes place when the quartz wedge is inserted 
normal to the length of the fibres, and the Tasmanian stichtite was 
found to behave similarly. Thus, as stated by Ward, the fibres are 
optically positive, measured with respect to their elongation. If, there- 
fore, the mineral is uniaxial, and the fibres are elongated in the direction 
of the principal axis, stichtite is optically positive, and not negative as 
would appear from Himmelbauer’s observations. Notwithstanding the 
basal cleavage, the writers have in no instance observed a fragment 
to give an interference figure, as might perhaps have been expected, 
