MINERALOGY OF BLACK LAKE AREA. 
77 
“Precious” or “Noble” Serpentine. 
Specimens of massive serpentine collected at the pits of the 
Megantic mine 1 are translucent, and have a somewhat waxy or greasy 
lustre and chrysoprase-green colour. The hardness is about 3J. Although 
the material appears quite compact, a determination of the specific 
gravity indicates that it is in reality somewhat porous. The value found 
immediately after immersion in water is 2 • 39, but the apparent weight 
of the substance continues to increase at a comparatively rapid rate, 
rendering an accurate weighing impossible. After boiling for about two 
hours, and allowing to remain overnight, still immersed in the water, 
the specific gravity was found to be 2*51, and it is possible that the true 
value is somewhat higher than this, and the same as that for the ordinary 
massive serpentine. 
Small veins of chromite are to be seen scattered through some speci- 
mens of this translucent material. The serpentine, in the vicinity of 
these chromite grains sometimes includes small patches or narrow 
veinlets of a deep lilac coloured mineral, which has been identified as 
stichtite, a rare chrome-bearing magnesium hydroxy carbonate, hitherto 
only recorded from Dundas, Tasmania. This mineral has been described 
on page 27. 
The composition of the precious serpentine is given in column 2 
above. So far as observed, this variety is rare within the area, and 
occurs only as very narrow veins. It has been previously recorded both 
by Cirkel* and by Jones, 3 the specimens in each case having come from 
the same locality as those here described. 
Porcellophite. 
A white, cream, or pale coloured material, usually very compact and 
clay-like, has been observed at several localities as one of the latest 
minerals to be formed. Its blowpipe and general physical characters 
indicate that it is a hydrous magnesian silicate, and, in many instances 
at least, it is probably to be referred to porcellophite, or some nearly 
related variety of serpentine. Among such occurrences may be ment- 
ioned that at the Montreal chrome pit, where it is associated with the 
lilac vesuvianite and colourless diopside. A similar substance, having 
a cream colour, is also found partly filling some of the druses in specimens 
of colerainite from the old Standard mine. 
Two specimens of this material have been analysed. One, from 
the Megantic mine, has a very pale grey colour, and the other, from the 
Hall chrome pit, is pale brown. Both are very compact, resembling dried 
1 Indicated by (2) on Dresser's map 23A, "Thetford-Black Lake Mining district.” 
*Chrysotil e-asbestos. Op. dt. p. 24. 
* Chryaotile-aabestos, Op. dt., p. 159 
