66 
MUSEUM BULLETIN NO. 27. 
Alteration Products. The fresh clinochlore is very easily cleavable 
into flakes, which are highly flexible; but altered forms occur in which the 
cleavage is poor, and the flakes become increasingly brittle ; at the same 
time, the crystals lose their bright bluish colour and exhibit instead paler 
green tints, until the most highly altered form is almost white, with a 
pale greenish tinge. Optically, these behave in the same way as the 
unaltered material, being biaxial with variable angle, but always positive 
in sign. Under the microscope, in parallel light, they are seen to be 
composed of the clear transparent clinochlore more or less filled with an 
opaque, granular or dusty decomposition product, which is white, and 
claylike by reflected light. All gradations are met with from the fresh 
crystalline material to that of this alteration product, which transmits 
practically no light. The fusibility becomes easier as the alteration 
proceeds, the fresh mineral being fusible with difficulty and only on the 
edges of thin flakes, while the yellowish-white material is fairly easily 
fusible, the result in each case being a white enamel. 
COLERAINITE. 
The area has afforded one new mineral species which occurs in 
definite, though minute, crystals in a pegmatitic vein at the old Standard 
mine and also in specimens collected from a dump near the Union pit. 
To this, the name colerainite has been given in reference to the locality 
of discovery. 
The best specimens were obtained from the dump at the old 
Standard mine, (Plate VIII B) and the following description refers more 
particularly to these. 
Crystals of colerainite have the form of extremely thin, hexagonal 
plates or flakes. In the best specimens collected these have a rather 
uniform diameter of about one mm., and they are so thin, that even when 
examined with a high power under the binocular microscope, no crystal 
facets can be seen between the two basal planes. As a rule the plates 
have a somewhat rounded outline, and are curved with a slightly concave 
upper surface; smaller flakes being arranged in more or less parallel posit* 
ion upon these, give rise to rosettes, which being frequently aggregated 
together in the form of spheres, give to the specimens a characteristically 
botryoidal structure. Less frequently, the crystals are attached to the 
matrix by an edge, and individuals have been able to develop more 
freely and perfectly. These are perfectly flat plates with a sharp hexa- 
gonal outline, and they often completely interpenetrate one another, 
bqt whether as a result of twinning or not could not be determined. 
The crystals occur, lining irregular and, in many places, large druses 
in a somewhat cavernous pegmatitic material, no doubt from a vein 
which intersected massive serpentine. They appear as a crust, 1 or 
