PYROXENITES OF THE GRENVILLE SERIES 321 



as amorphous chemical sediments, which under moderate heat and 

 pressure arranged themseh^es and crystalhzed, generating the various 

 mineral species by a change which Giimbel designates diagenesis . 

 The apatite deposits were regarded by Hunt' as vein formations 

 resulting from hot-water solutions, though some were thought to 

 occur in beds. The belief as to the vein origin of these deposits was 

 based on the following considerations: (i) the rounded form of the 

 apatite crystals, which he considered due to partial solution after 

 deposition, rather than to fusion in a molten magna; (2) the manner 

 in which one mineral incloses another, as in the case of crystalline 

 calcite, rounded into pebbles and inclosed in the center of apatite 

 crystals; (3) the banded structure observed in some deposits; (4) 

 drusy cavities. The banded arrangement is not a frequent charac- 

 teristic of the deposits, but is sometimes seen. Dawson considers 

 many of the Ontario deposits as true beds and of organic origin, 

 thus apparently postulating a sedimentary origin for the inclosing 

 rocks,'' though not necessarily for all of them. 



Harrington, in his admirable report on the apatite-bearing veins 

 of Ottawa county, takes the same view as to the origin of the pyroxe- 

 nites, and contends that the conclusions of Brogger and Reusch 

 concerning the eruptive origin of the apatites of Norway do not apply 

 to the Canadian occurrences. He adds: 



The pyroxenites often contain disseminated grains of apatite, and no doubt 

 they are the strata from which the apatite of the veins has been chiefly derived. 

 If, as has been suggested, the apatite of these ancient strata represents material 

 accumulated by organic agencies, then the connection of the pyroxene and apatite 

 may be that the former constituted an ocean bottom particularly suitable for the 

 life of the creatures which secreted the phosphatic matter. 



W. Boyd Dawkins,3 who visited this locality in 1884, adopts 

 Harrington's conclusions, though he adds: "Were it not that it is 

 bedded, it would pass muster as an eruptive rock." He concludes 

 that the apatite deposits were formed in fissures in the Archean 

 gneisses by hydrothermal or aquo-igneous action under conditions 



^ Geology of Canada, 1863 pp. 477, 644; American Journal of Science, 2d ser., 

 Vol. XXXVII, p. 252; Chemical and Geological Essays, p. 208. 



- Sir J. W. Dawson, Quarterly Journal of the Geological Society, Vol. XXXII 

 (1876), p. 289. 



3 Proceedings of the Manchester Geological Society, December 2, 1884. 



