42 The Ottawa Naturalist. 



The epidote and zoisite occur in irregular, often somewhat elongated 

 masses or "grape-like" bunches which frequently show a more or less 

 definite arrangemenr in accordance with the structure of the original 

 felspar. Both minerals exhibit theii characteristic high relief, the epi- 

 dote showing brilliant chromatic polarization colours, and yellow to 

 colourless pleochroism, while the interference colours of the zoisite, as 

 usual, are very low, dull bluish to yellowish. The sericite is of a very 

 pale green, and occurs in scales or aggregates of scales and plates, show- 

 ing customary brilliant polarization colours and parallel extinction. The 

 sericite has, likewise, often a definite arrangement, but sometimes occurs 

 in irregular or matted aggregates. The " saussuritization " of the origi- 

 nal plagioclase has been usually so complete, that only traces of the 

 twinning lamellae can be detected. The matrix in which these crystals 

 are embedded is a diabase, composed essentially of plagioclase and 

 augite. The plagioclase shows moie or less alteration, identical in cha- 

 racter with that of the larger phenocrysts so that it must have had a 

 similar composition. It occurs as lath-shaped, twin crystals, often con- 

 sisting of only two lamellae, which pierce, and are often embedded in the 

 augite. The augite occurs in more or less irregular masses, filling in 

 the interstices between the felspar laths. It is light brownish in colour, 

 exhibits a faint pleochroism, and the characteristic interrupted cleavages 

 in cross-section. It is partially altered into green trichroic hornblende, 

 and occasionally the alteration has been carried so far that chlorite has 

 resulted. This uralitization has only proceeded to a limited extent. 

 and is confined to a narrow margin surrounding the irregular fissures 

 traversing the augite masses. Occasional twins were noticed, the 

 twinning plane being the orthopinacoid. 



Ilmenite is abundant, but almost wholly converted into leucoxene- 

 The fragments have generally jagged and irregular contours, hut occa- 

 sionally, some are seen which possess a rather perfect crystallographic 

 outline. The characteristic alteration along lines parallel to the faces 

 of the rhombohedron produces alternating bands of greyish white leu- 

 coxene, and black, unaltered ilmenite. The less altered portions of 

 the plagioclase and the augite show uneven or wavy extinction, the 

 " strain shadows " induced in the latter being especially well marked, 



