86 



KEMPS ORE DEPOSITS. 



ANALYSES OF LIMONITES. 



2.01.26. All published analyses, except when forming a suffi- 

 ciently large and continuous series from the output of any one mine, 

 are to be taken with caution. Ores necessarily vary much, and a 

 single analysis or a selected set may give a very wrong impression. 

 The percentage in iron is different for different parts of the same 

 ore body. The few that follow have been selected to show the 

 range and the average. The highest are exceptionally good, the 

 lowest less than the average, and the medium values indicate ap- 

 proximately the general run. Limonites afford from 40 to 50g Fe 

 as actually exploited, but it is not difficult to find individual analy- 

 ses that run higher. They are not, generally speaking, Bessemer 

 ores. 



Analyses of Limonites. 



SIDERITE, OR SPATHIC ORE. 



2.01.27. Siderite is the protocarbonate of iron. As a mineral 

 it often contains more or less calcium, magnesium, and manganese. 

 When of concretionary structure, embedded in shales and contain- 

 ing much clay, the ore is called clay ironstone. When the concre- 

 tions enlarge and coalesce, so as to form beds of limited extent, 

 generally containing much bituminous matter, they are called 

 black-band, and are chiefly developed in connection with coal 

 seams. 



2.01.28. Example 3. Clay Ironstone. The name is applied to 

 isolated masses of concretionary origin (kidneys, balls, etc.) which 

 may at time coalesce to form beds of considerable extent. They 

 are usually distributed through shales, and on the weathering of 

 the matrix are exposed and concentrated. They are especially 



