June, 1906. New Forms of Concretions — Nichols. 45 



Analysis of the Centre of a Nodule from the Challenger 



Bank. 



CaO 49-66 



CO ? 42.92 



MgO 2.38 



Na 2 0.34 



MnO 0.05 



FeO 0.12 



Al 2 O a 0.58 



Si0 2 o . n 



SO, 0.55 



P 2 5 0.02 



CI 0.37 



Loss in ignition* 2 . 93 



100.03 

 Less O A Cl 2 o . 08 



99 • 95 

 This corresponds to: 



Calcium carbonate 88 . 61 



Magnesium carbonate 4-98 



Ferrous carbonate , 0.21 



Manganese carbonate o . 08 



Miscellaneous, 6 .07 



99-95 

 A magnesia determination was also made upon about two grams 

 of the extreme outer portion of the nodule. 5.12% of magnesia was 

 found, corresponding with 10.70% of carbonate of magnesia. Thus 

 it appears that the exterior of the nodule is more magnesian than the 

 interior. 



Inasmuch as the nodules occur isolated on a small bank in the 

 midst of the Atlantic, away from any possibility of impregnation 

 or alteration by waters flowing from pre-existing mineral veins, the 

 presence or absence of minute proportions of the heavy metals is of 

 importance as it bears directly upon the much disputed question of 

 the origin of ore deposits by lateral secretion or ascension. The 

 isolation of the material removes wholly the serious doubt present in 

 most determinations of this character as to whether any metals 

 found may not have originated in mineral veins and later impregnated 

 the surrounding rock. Consequently a search for traces of copper 

 and lead in thirty-seven grams of the nodule material was carried out 

 with great care. There was not a trace of either metal present. 



*LessC02. Chiefly organic matter and some water. The organic matter makes itself very 

 evident upon igniting the specimen, both by its odor and by blackening. 



