268 ANALYSES OF SOME CANADIAN MINERALS. 



7. Ilanganese OcJire : from north-east side of Thunder Bay, Lake 

 Superior. 



This is an earthy mixture of iron and manganese ochres containing 

 an unusually small amount of water. I did not collect the sample per- 

 sonally, but I am informed that it came from a bed of considerable 

 extent on the shore of the Pay. When sent to me, it was in the form 

 of a dry coarse powder of a dark brown colour. The colour is scarcely 

 changed, after even long ignition in the air. The analysis yielded : 



Sesquioxide of iron 33-68 



Sesquioxide of manganese ... 22-18 



Lime 0-81 



Carbonic acid 3-78 



Water 3-82 



Insoluble rock-matter 3612 



100-39 

 It is evident however that part of the manganese (with perhaps a 

 portion of the iron) is present in the state of carbonate. The analysis 

 might therefore be written more correctly as follows : 



Sesquioxide of iron 33-68 



Sesquioxide of manganese.. 16-54 



Protoxide of manganese ... 5-08) ^^ , . n .^o 



^. /^ o-i f j Carbonate manganese... b-2d 



„ \ . ., o tt-Q \ 1 Carbonate of lime 1-44 



"Carbonic acid o'/o ; 



Water 3-82 



Insoluble rock-matter 36-12 



99-83 



The water and carbonic acid are determined in a separate portion of 

 the substance, the values, given above, being the mean of two deter- 

 minations. Special tests for sulphuric and phosphoric acids shewed 

 the presence of these bodies in very slight traces. 



The less exposed portions of this ochreous deposit would probably be 

 ifound to consist very largely of carbonates. 



