I9I4.] CONCEPTION AND TRINITY BAYS, NEWFOUNDLAND. 441 



all events, to explain the percentages as brought out in the analyses. 

 It would seem then that the ferric iron does not exist essentially as 

 hematite but as a silicate or some other allied mineral, and that 

 the green color so predominant in the manganese bands and shales 

 may be due to the ferrous and ferric silicate. 



The presence of hematite in the red band has undoubtedly caused 

 the red coloration and the same may be said in reference to the red 

 shale, 2IO A 4, where there is an excess of .72 of FeO over the 

 Fe203, but in these there undoubtedly has been sufficient masking 

 of the ferrous and ferric silicates of iron by the hematite. 



The production of the hematite was probably brought about by 

 the conversion of the silicate into Fe203 through oxidation. 



VII. GENESIS OF THE MANGANESE DEPOSITS AND ASSO- 

 CIATED MINERALS. 



So many of the sedimentary manganese deposits described in 

 the literature are in such a highly altered condition because of 

 oxidation and deeper seated metamorphic influences whereby the 

 original or primary manganese minerals have been so altered as to 

 be of little genetic significance, that the carbonate-oxide manganese 

 ores of southeast Newfoundland, Avhich are surely primary ores, 

 give promise of yielding evidence of considerable value on the 

 question of genesis. In considering the genesis of any marine sedi- 

 mentary manganese deposits, we are, however, confronted with 

 many grave difficulties because we are dealing with submarine 

 chemical conditions of which little is known and with diagenetic 

 processes of which still less is known. It is also very difficult to 

 advance any suitable chemical hypothesis founded upon some re- 

 action that successfully works out in the laboratory which will not 

 be of doubtful application in nature. With these difficulties in mind 

 the following subjects relating to the genesis of the manganese 

 deposits of southeast Newfoundland will be considered : Early 

 Cambrian physiography ; Nature of deposited sediments ; Condi- 

 tions under which the manganese deposits were formed ; Summary 

 of genesis of manganese; Diagenetic structures, as banded, nodular 

 and oolitic ; Genesis of barite ; Genesis of tricalcium phosphate ; As- 

 sociation and separation of iron. 



