216 GRANITES AND GRANITIC VEIN-STONES. [XI. 



crystals having rounded angles, octahedrons of magnite, al- 

 lanite, and a soft greenish mineral resembling loganite. 



46. As regards the order of deposition of minerals in 

 these veins, we find apatite enclosed alike in calcite, in quartz, 

 in phlogopite, in spinel, in graphite, and in pyrite. On the 

 other hand, apatite sometimes includes rounded crystals of 

 calcite or of quartz j and graphite, which itself encloses apatite, 

 is found included alike in quartz, in orthoclase, in pyroxene, 

 and in calcite, in such a manner as to lead us to conclude that 

 its crystallization was contemporaneous with that of all these 

 minerals ; while from the other facts mentioned it would appear 

 that the order of deposition was subject to variation and to 

 alternations. In a vein in Grenville large prisms of a white 

 aluminous pyroxene (leucaugite) penetrate great crystals of 

 phlogopite, while at the same time small crystals of a similar 

 mica are completely imbedded in the crystallized pyroxene. 

 Many facts relating to the association of various species in 

 these vein-stones will be found in my essay, but the subject is 

 one which still demands careful study. The banded structure 

 of these veins is well shown in some of those which contain 

 graphite. This mineral, though sometimes irregularly dissemi- 

 nated through the vein-stone, frequently occurs in sheets or 

 layers alternating with orthoclase, quartz, or pyroxene, parallel 

 to the walls of the vein and exhibiting a peculiar structure due 

 to the formation of successive layers of crystalline lamellae 

 more or less nearly perpendicular to the plane of deposition. 



47. The veins hitherto noticed, whether feldspathic or 

 calcareous, are generally vertical, or nearly so, and in most 

 cases traverse the stratification. Of many of them which have 

 been explored to some extent for apatite, mica, and graphite, it 

 is noticed that they are subject to great changes in dimension 

 as well as in mineral contents. They often appear to occupy 

 short irregular fissures, and in some cases are to be described 

 as more or less completely filled geode-like cavities rather than 

 veins. 



48. In the reprint of my essay, already mentioned, s"\vrul 

 veins are noticed in the county of Hastings, Ontario, in rocks 



