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TE ee Sc eee eed 
344 Canadian Record of Science. 
North of Vermilion River, near Booth and Hales’ lumber 
camp, examples were obtained of the remarkable black 
voleanic breccias described by Dr. Bell and the two distin- 
guished petrographers before mentioned. Prof. Williams 
describes under the name of a vitrophyre tuff’ specimens 
enclosing angular fragments of glass or pumice, turned 
into chalcedony, or a mosaic of small quartz individuals, or 
sometimes a greenish mineral or even a calcite individual. 
In some of my sections enclosed fragments have been 
turned into a brownish green substance with faint double 
refraction, probably serpentine, but possibly chlorite. 
_ Other fragments are now made up of radiating crystals of 
epidote. One large white fragment turns out to be a micro- 
granite consisting of quartz, orthoclase, microperthite and 
plagioclase with a little serpentine. Still other enclosures 
are of clear quartz individuals, at times with hexagonal 
outlines. The fluidal and vesicular structure of many of 
the fragments corresponds exactly with Prof. Williams’ 
description and figure. 
East of the lumber camp and south of Clear Lake gabbro 
makes its appearance, fine grained and dark green on fresh 
surfaces, but weathering to pale greenish grey when free 
from sulphides, and to various tones of brown when 
charged with them. This rock differs greatly from the 
green diabase, etc., found nearer Sudbury. In most thin 
sections the felspars are not lath-shaped, but have short 
idiomorphic forms, sometimes apparently of a single indivi- 
dual or in halves like Carlsbad twins, but generally showing 
several twin lamellae. The angle of extinction from the 
twin plane is generally large, 25° or 30°, but at times only 
5° or 10°. No anaiysis was made to determine the presence 
or absence of orthoclase. The other minerals are chiefly 
varieties of pyroxene, especially diallage and enstatite, 
greatly weathered to greenish chloritic products, which 
have frequently been deposited between the felspars. 
Large stout crystals of apatite occur in one thin section, 
and pyrrhotite forms a large part of some specimens. An 
1 Sudbury Mining District, p. 74, etce 
