CHEMICAL RELATION OF IRON AND MANGANESE. 365 



about most easily at high temperatures. It has also been noted 

 that when manganese, in the form of the alloys spiegeleisen 

 and ferro-manganese, is added to molten steel, it bodily removes 

 a part of the sulphur ; and it is thought by some metallurgists, 

 that sulphide of manganese is formed and carried into the slag. 



These and other indications of the more easy ti^ansition of man- 

 ganese into the form of sulphide at high rather than at low tem- 

 peratures afford another cause which might prevent sulphide of 

 manganese from being formed in sedimentary deposits, for such 

 deposits are usually laid down at ordinary temperatures. On the 

 other hand, they also afford a cause which might lead to the 

 deposition of the sulphide of manganese in certain metalliferous 

 veins and other deposits, where the temperature at the time of 

 deposition may have been high. 



In many of the silver and lead deposits of the Rocky Moun- 

 tains manganese oxides occur with the superficial oxidation prod- 

 ucts of the sulphides of other metals, and it has often been 

 suggested that the manganese also was originally in the form of 

 sulphide. This may be true in some cases, for alabandite has 

 been found in a few metalliferous deposits in Colorado, Mexico, 

 Germany, Peru and elsewhere, but in most cases, at least in the 

 Rocky Mountains, when the level is reached at which the 

 oxidized forms of lead, zinc, iron and other metals pass into 

 sulphides, the manganese passes into carbonate or silicate, and 

 remains in one or both of those forms to all depths that have 

 been reached. 



In the deposition of iron and manganese as sulphide, therefore, 

 there is a most marked difference of behavior, and here again is 

 a good cause for the separation of the two substances in sedi- 

 mentary rocks, as will be more fully explained below. 



Iron is often deposited in sedimentary formations as the 

 hydrous silicate of iron and potash known as glauconite, and 

 composes the mass of the large greensand beds common in Cre- 

 taceous and Tertiary strata ; but manganese is not found in an 

 exactly similar condition.^ Here again, therefore, is an import- 



' Manganese occurs in various hydro-silicates, but tliey do not appear to be 

 deposited as sedimentary strata in the same manner as glauconite. 



