USEFUL METALS 



follows: (1) Manganese ores. (2) Manual liiVmu- imn ores. 

 (3) Manganiferous silver ores. (4) Manganifcrous xin< n-.-iduum. 

 The manganese ores proper comprise tin- high-grade pyrolu-ite 

 and polianite that are reasonably free from iron. The Bra/ilian 

 ore, psilomelane, meets this demand as will be seen later in tin- 

 discussion of its composition. 



The manganiferous iron ores consist largely of limonite and 

 hematite bearing certain quantites of pyrolusite, psilomelane, or 

 even wad. The higher grade ores of this class find use in the 



FIG. 124. Section exposed in a pit in the Dobbins mine in Georgia. 

 The black bands represent manganese ore and the shaded portion clays. 



(After Penrose.) 



manufacture of ferromanganese and spiegeleisen for the manufac- 

 ture of steel. 



The manganiferous silver ore consists of manganese and iron 

 oxides bearing a sufficient amount of silver to pay for its profitable 

 extraction. Gold is sometimes present in these ores and not 

 infrequently the carbonate of lead. The ores in this class that are 

 the richest in silver and lead are used for the extraction of thrsc 

 two metals. The iron and manganese content sometimes assures 

 a higher price because of their fluxing properties. If the silver 

 and lead content is too low to pay for the profitable extraction of 

 these metals but rich in their iron and manganese content they 



