GAGE IRON ORES IN MISSOURI. l8l 



On the Occurrence of Iron Ores in Missouri. 

 Bj Jas. R. Gage, M. E., 



ASSISTANT STATE GEOLOGIST OF MISSOURI. 



During my connection with the State Sui"vey I have made a 

 collection of the Iron-ores, which I wish to donate to the Society, 

 and at the same time would make a few remarks upon the occur- 

 rence of these ores. 



There are but four ores fro m which iron is extensively derived, 



viz. : 



Spathic Iron (Carbonate of Iron, iron spar) ; 

 Red Hematite (Specular, Oligist, iron glance) ; 

 Brown Hematite (Limonite, bog-ore, hydrous oxide) ; 

 Magnetite (magnetic iron). 



As the first mentioned ore has as yet not been found in sufficient 

 quantities in this State for mining purposes, we will now pass to 

 the consideration of the three latter in regard to their geological 

 position and occurrence in Missouri. 



These Iron-ores are found in what are known in Missouri as 

 the Saccharoidal Sandstone, 2d Magnesian Limestone, and 2d 

 Sandstone (all of which are included in the Lower Silurian for- 

 mation), and in the Porphyries which geologically lie below and 

 belong to the Primary or Palaeozoic age. These ore deposits are 

 found in the above-mentioned rocks, and appear as veins, lodes, 

 beds, segregations and impregnations, and may be the result of 

 direct precipitation from a solution, especially in cases where 

 they occur as beds, or from a variety of causes, all of which we 

 will consider. 



Theories in explanation of vein-formations were offered almost 

 as early as Geology may be termed a science. From the time of 

 Agricola, who was the first to propound a theory, down to the 

 time of Werner and Hutton, who systematized Geology and re- 

 ally established its claims to be ranked as a science, each has 

 had a theory to account for the origin of vein-formations ; some 

 of which we will now examine, and see if any is sufficiently well 

 supported by facts to explain the vein ore-deposits in Missouri. 



According to Cotta's classification, in his work entitled Erzla- 

 gerstdttenlehre^ they are divided as follows : 



I. Theory of Contemporaneous Formation : the lodes are not mineral mat- 

 ter filling fissures, but were formed synchronously with the enclosing 

 rock, or subsequently by a metamorphosis of the altered regions of the 



