OXIDES 



as inclusions, are colored red by them. Indeed most of the red 

 mientary rocks are colored with hematite, as jaspers, sand- 

 stones, shales, and clays. 



The most important deposits of hematite are associated with 

 sedimentary rocks, where the layers of hematite are interbedded 

 with chert, jasper, shales, and sandstones. These deposits, have 

 been derived from the chemical precipitation of Fe 2 3 resulting from 

 the oxidation of ferrous carbonate in solution. These precipitates 

 gather in layers at the bottom of drainage basins, their physical 

 condition depending upon future metamorphism to hematite. 

 Such are the fossil and oolitic hematites connected with the 

 ( 'linton formation, extending from New York to Alabama. 



In the Lake Superior region the oxidation of silicates, pyrite, 

 and carbonates has filled an important r61e in the formation and 

 concentration of enormous deposits, which have yielded millions 

 of tons of ore, but like the Clinton ores they are connected with 

 sedimentary formations. In the oxidation and replacement pro- 

 cesses hematite may form pseudomorphs after pyrite, calcite, sider- 

 ite, magnetite, quartz, and fossils, especially shells. A variety of 

 Fe 2 O 3 , martite, occurring in large octahedrons at Twin Peaks, 

 Mallard County, Utah, is possibly magnetite oxidized to hematite. 



Eighty per cent, of all iron ore mined in the United States is 

 hematite, most of which is taken from the Lake Superior region, 

 where it is mined in large open quarries, as it lies near the surface. 

 The principal localities are Marquette, Menominee, and Gogebic, 

 Wisconsin ; Vermilion and Mesaba districts of Minnesota ; and the 

 Northern Peninsula of Michigan. In the East hematite is mined 

 at various points along the Clinton formation. Large deposits also 

 occur at Iron Mountain, Missouri ; in Wyoming; while Nova 

 Scotia and Newfoundland supply the Canadian industries. The 

 best crystalline specimens are obtained from the Isle of Elba ; 

 from Cumberland, England, where it is associated with quartz and 

 dolomite ; at St. Gothard, Switzerland, in rosettes and in flat tabular 

 scales associated with rutile crystals. Large rosettes five or six 

 inches across are obtained from Brazil. 



Artificial. Micaceous hematite crystals may be formed by 

 heating a concentrated solution of ferrous sulphate with copper 

 sulphate in a sealed tube for 10 hours at a temperature of 210. 



Fe 2 O 3 when fused loses oxygen and' on cooling forms magnetite. 

 On fusing ferric oxide and borax and dissolving the melt in hot dilute 

 HC1 crystals of hematite will be left. 



