88 
Journal of the 
for the crystallisation of the hornblende to have impressed its own 
form upon it. (Fig. No. 9.) 
The hornblende includes, or is accompanied by grains or masses 
of magnetite, which constantly show rectangular sections or forms 
compounded of rectangular outlines. With the exception of the 
granules of ground-mass which I have mentioned, there are no 
inclusions Which I have observed in the hornblende. 
The alteration to which the hornblende is liable is the production 
of chlorite. What this form of chlorite is I am unable to say. 
Its character is more that of flakes than of fibres. It is slightly 
dichroic, and so far as I could observe, identical with the minute 
flakes of chlorite, which are of very frequent occurrence in the 
mass of dykestone. 
As I have before stated, a gradation of forms may be observed 
from the unmistakable hornblende down to microliths in the 
ground-mass. But the two extremes are distinguished by the 
generally fibrous aspect and polycliroic properties of the former 
being doubtful, if not absent, in the latter. 
The finely crystalline portion of dyke in the hill north of 
Bulgoback Creek I found to consist of crystals of triclinic felspar 
and hornblende, with a little magnetite. As might be expected 
from the crystalline texture of the stone the hornblende is here 
much more perfectly crystallized than is usually the case. It occurs 
in long thin prisms, cross sections of which show the characteristic 
prismatic cleavage of hornblende. 
The constant occurrence of magnetite with and in the hornblende 
su gS es *ts that it may represent the excess of iron beyond the 
amount required in the composition of that silicate. 
(c). Magnetite . — From previous statements it will be seen that 
magnetite is of frequent occurrence. It is found not only closely 
connected with the hornblende but also plentifully scattered through 
the ground-mass, and more rarely it occurs in the felspars. It is 
of least frequent occurrence in the minute flakes of brown mica. 
Some of the black opaque rectangular substances may, however, 
belong to titanic iron, or to pyrite. 
(cl). Mica .—Mica is rare as minute brown flakes, and is quite 
subordinate to the other constituents. Its form, colour, and 
optical properties indicate it as being a magnesia mica. 
(e). Apatite . — The colourless prisms, withplain terminations, as 
