22 
MUSEUM BULLETIN NO. 27. 
BRUCITE. 
Brucite occurs as an alteration product of the serpentine, and is 
probably widespread in the area, though specimens were collected from 
only two or three localities. 
At the American asbestos pits this mineral occurs lining fissures in 
the massive green serpentine, which is also traversed by veins of chry- 
sotile asbestos. The brucite crystals, having a diameter of about 1 mm., 
are colourless and transparent, with a pearly lustre on the basal plane, 
which is usually triangular in outline. The crystals are not sufficiently 
good for goniometric measurement, but examination under the bino- 
cular microscope shows them to be combinations of the rhombohedra 
r(1010) and p(2021) with the basal pinacoid. Associated with the 
crystals there is frequently a white pulverulent product, and generally 
also hydromagnesite in white adcular needles forming radiated groups. 
Other specimens were collected by Mr. Jos. Johnston from the 
Consolidated Asbestos and Chrome property, where they occur in a new 
pit operated by Mr. Chretien. There the brucite occurs as veinlets, 
both in the serpentine and in massive chromite, forming foliated masses 
having a somewhat feathery appearance due to a radial arrangement 
of the cleavage plates. Normal to the cleavage, these flakes are colour- 
less and have a pearly lustre, but when viewed transversely the mineral 
has a greenish colour and dull lustre. When the fissures are irregular, 
especially in the chromite, minute crystals of similar habit to those 
described above are found. Associated with the brucite are small 
octahedra of magnetite, rosettes of aragonite, and the alteration products 
already referred to. A similar occurrence to the last, in which brucite 
is associated with serpentine and chromite, is that at the Martin Bennett 
property. Reference has already been made to this under chromite. 
A very interesting specimen of brucite, pseudomorphous after 
chrysotile, was received by the writers from Professor C. Palache, who 
had collected it in 1913 when he visited the asbestos district with one 
of the Geological Congress excursions. The exact locality for this is 
not known. The specimen, of a bluish-green colour, is composed of fine 
fibres, packed closely together in parallel position, and having a length 
of about 3 cm. Examination shows the fibres to be largely brucite 
(nemalite) but, in part also, and especially toward the extremities of the 
fibres, they are chrysotile. There is sufficient hydromagnesite present 
to cause the material to effervesce when treated with hydrochloric acid ; 
on warmirig, the brucite also dissolves, and fine threads of chrysotile are 
left insoluble. It is clear that the material was originally a vein of 
chrysotile, which subsequently underwent alteration, fibre by fibre, ' 
each from its surface inward, to brucite, although in the specimen 
