OEE DEPOSITS OF UPPER HUEONIAN. 



181 



slates of the Upper Marquette series, but dififer very considerably from those 

 of the Lower Marquette series, in which the hard hematites and magnetites 

 are important ores, and from the ores of the Menominee district, which pro- 

 duces large quantities of soft blue hematite, some martite, and also some 

 specular ore. 



The following figures show the average composition of the ores for the 

 district. They were taken from analj^ses furnished by the management of 

 the various mines and from the reports of the State commissioner of mineral 

 statistics of Michigan. 



The me'tallic iron of the ores ranges from 54 to 63 per cent, the aver- 

 age being about 59 per cent. Phosphorus in exceptional cases is as low 

 as 0.05 per cent, though usually ranging from 0.1 to 0.7 per cent, most com- 

 monly approaching the higher figure. Silica averages about 3 per cent. 

 These analyses show the ore to be rather low grade.^ It is due to this that 

 this district has been so sensitive to the prices of iron ores. A low market 

 price makes the cost of production exceed the selling value, and under 

 these conditions work necessarily stops. 



Some of the ores in the Crystal Falls disti-ict contain a very high 

 percentage of AlgOg, CaO, and also of manganese. It is reported that 

 some very good deposits of manganese have been found, one unauthenti- 

 cated statement being to the effect that an analysis of the ore runs as follows: 

 Metallic iron, 17.46; manganese, 29.81; phosphorus, 0.064; sihca, 0.009(?). 



' Brooks states that " the ores are unlike those in the more easterly part of the Menominee region 

 in being richer in iron, freer from silica, and in containing more water." (Analysis 68, p. 302.) Geol- 

 ogy of Michigan, Vol. I, part 1, p. 182. 



Since the above was written the volume on Mineral Resources of the United States, 1896, Part 

 V, of the Eighteenth Annual Report of the United States Geological Survey, has appeared, and the 

 following analyses of ores from the Crystal Falls district are taken from Mr. John Birkiubine's article 

 on iron ores in that report. 



The analyses were prepared for the ore association at Cleveland, Ohio, and show the average 

 cargo analyses of iron ore as shipped from the various mines. The analyses were made from ores 

 dried at 212^^, the amount of natural moisture being added. 



