Excerpt from Reports on a Portion of Algoma and Thunder Bay Districts, Ontario, And, on the Region Lying North of Lake Superior Between the Pic and Nipigon Rivers, Ontario The feldspars which so largely compose the rocks, comprise plagioclase, orthoclase and microcline. Both monoclinic and triclinic varieties are always present, the relative amounts varying from sec tion to section. In general the amount of microcline, as compared with that of orthoclase, increases with increasing deformation of the rocks as the result of pressure. Quartz is always abundant, but occurs in varying amounts. Amongst the accessory minerals, apatite, pyrite and magnetite are often present. Grains of sphene are common. Allanite occurs in a number of sections sometimes included in irregular grains of epidote, sometimes alone. Garnets occur in only two sections. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.