The Phosphates of America. 27 



CHAPTER III. 



THE PHOSPHATES OF NORTH AMERICA. 



THE greatest of our geologists have agreed upon dividing the 

 earth's crust into four classes or periods, which they have named 

 respectively the Archaean, Paleozoic, Mesozoic and Cenozoic times, 

 and the phosphates which we are now to describe occur in the 

 rocks of the first of these divisions, in that portion of them known 

 as the Gneiss formation or Laurentian period. 



These rocks are made up almost entirely of pyroxene, calcite, 

 hornblende, mica, fluor-spar, quartz and orthoclase, and are more 

 or less intermixed at various points with apatite, pyrites, graphite, 

 garnet, epidate, idocrase, tourmaline, titanite, zircon, opal, calce- 

 dony, albite, scapolite, wilsonite, steatite, chlorite, prehnite, chaba- 

 site, galena, sphalerite, molybdenite, etc. 



The two districts in Canada in which apatite has been thus far 

 found to exist in workable quantities are Ottawa County, in the 

 province of Quebec, and Leeds, Lanark, Frontenac, Addington and 

 Renfrew Counties, in the Province of Ontario. The latter district, 

 therefore, covers a much larger area than the former, but on the 

 other hand the country is much lower, the rocks more hornblendic 

 and the apatite much more "pockety" and scattered. In both dis- 

 tricts the Laurentian rocks form immense belts, which traverse the 

 country for many miles with a N. E. and S. W. trend, and which, 

 according to Dana, Hunt and other investigators, extend downward 

 to a depth of at least twenty-five or thirty thousand feet. There 

 is, as may be readily inferred, a great variability in their composi- 

 tion. Sometimes they are entirely granitic gneiss, hornblendic 

 gneiss, rust-colored gneiss and brownish quartz ; at others they 

 are made up of pyroxene, feldspar, calcite, mica, apatite, and py- 

 rites. While there are undoubtedly many spots in which the apa- 

 tite would appear to occur in true veins of extreme purity, we 

 have found that the general formation of the fissure material is 

 that of a series of conglomerates. In other words, the gigan- 

 tic lodes are a mixture in which the predominance alternates between 

 pure apatite and pyroxenite or mica, or feldspar, or, in fact, any 

 other of the minerals already enumerated. 



