THE IRON SERIES, CONTINUED. 99 



2.02.12. Example 7. Crawford County, Missouri. Bodies of 

 specular and hard and soft red hematite, associated with clay and 

 chert, and filling cone-shaped (base down) or rude cylindrical 

 depressions in the Second Sandstone of the Missouri Cambrian. 

 The hard and soft hematites have resulted from the alteration 

 of the specular. Clay and chert always accompany the ore, and 

 with it fill the cavities in the broken and faulted Second Sand- 

 stone. The deposits are distributed over several counties in cen- 

 tral Missouri, of which Crawford, Dent, and Phelps are the most 

 productive. The ore, etc., was thought by A. Schmidt of the Mis- 

 souri Survey (Rep. 1878, p. 66) to have either replaced the pre- 

 existing rock or to have been deposited in the hollows at the then 

 existing surface. Pumpelly, however, regards the iron as having 

 been derived from the weathering of the overlying First and 

 Second Limestones, to whose decay he likewise attributed the 

 clay and chert. The latter, it may be remarked, very generally 

 mantle southern and central Missouri, and it is probable that the 

 rocks have not been submerged since Paleozoic times. Much of the 

 drainage, it is thought, passed off through subterranean channels 

 forming caves in the Third Limestone. To the collapse of these is 

 attributed the formation of the cavities, in which the ores were 

 laid down with the residual clay, etc. 1 The region has afforded from 

 100,000 to 200,000 tons of ore annually. 2 



2.02.13. Examples. Jefferson County, New York. Beds of 

 red hematite, with more or less specular, lying beneath sandstones 

 of the Potsdam stage and associated with serpentine, crystalline 

 limestone, and other sandstone beds of uncertain relations. Not 

 far aAvay the Laurentian gneiss outcrops, although nowhere as- 

 sociated with the ores. The beds occur along a northeast belt from 

 Philadelphia, Jefferson County, to Gouverneur, St. Lawrence 

 County. They range up to 30 feet in thickness, and consist mostly 

 of red, earthy hematite with included masses of specular. Many in- 

 teresting minerals (siderite, millerite, chalcodite, quartz, etc.) are 

 found in cavities. Brooks gives the following geological section. 

 1. Potsdam sandstone, 40 feet. 2. Hematites, 40 feet. 3. Soft 

 schistose, slaty, green magnesian rock with pyrite and graphite 

 (thought by Emmons to be igneous), 90 feet and more. 4. Granular, 



1 R. Pumpelly, Tenth Census,Vo}. XV., p. 12. 



2 W. M. Chauvenet, Tenth Census, Vol. XV., p. 403 ; see also Pum- 

 pelly's paper, p. 12. A. Schmidt, "Iron Ores and Coal Fields," Missouri 

 GeoL Survey, 1874, p. 124. F. L. Nason, Idem., Vol. II., 1892, p. 116. Rec. 



