REVIEWS 197 



It is not possible to give a generalized section of the strata in east 

 Tennessee because of the local variations in the sequence. The ores are 

 contained chiefly in the "Rockwood" formation (Silurian). They are 

 found also in the Tellico sandstone (Ordovician) and to a very minor 

 extent in the Grainger shale (Devonian and Mississippian). Two wide- 

 spread formations, the Knox dolomite (Cambrian and Ordovician) and 

 the Chickamauga limestone (Ordovician), occur below the Tellico and 

 "Redwood." The Chattanooga shale (Devonian) and the Newman 

 limestone (Mississippian) which lie above the "Rockwood" are impor- 

 tant, the former as a reference horizon for the "Rockwood" ore and the 

 latter as a source of the limestone for fluxing material in the iron industry. 



In general the beds of the Cumberland Plateau are nearly horizontal, 

 while those of the Great Valley are tilted, folded, and faulted. 



The term iron ore as used in this report includes that which runs 

 20 or more per cent metallic iron. The red ores consist essentially of 

 hematite; the impurities are calcium carbonate, silica, alumina, magne- 

 sium carbonate, sulphur, phosphorus, and manganese. 



The Tellico ore varies from a ferruginous sandstone to lenses of com- 

 pact rich ore. The deposits near Riceville, near Sweetwater, and east 

 of Knoxville (here the ore is dominantly limonite) are described; the 

 two last mentioned are residual deposits. 



The "Rockwood" formation is composed of lenses of sandstone, 

 shale, limestone, and hematite; its thickness varies from a few feet to 

 over 1,000 feet. The ore beds are mainly in the upper 60-200 feet. 

 The ore is "a mixture of fossil fragments and flaxseed-shaped grains." 

 The soft ore (due to the leaching of calcium carbonite from hard ore) 

 carries 40 to 58 per cent metallic iron, while the hard ore runs from 25 

 to 45 per cent metallic iron. It is believed "that the 'Rockwood' iron 

 ore was formed by the deposition in a body of water of sediments con- 

 taining iron, together with calcium carbonate, silica, alumina, and other 

 minerals in minor proportions." Later much of the calcium carbonate 

 of the fossils was replaced by iron oxide; this may have occurred even 

 before the consolidation of the strata and "it probably involved only the 

 original sediments." The "Rockwood" ore outcrops more or less con- 

 tinuously along the base of the Cumberland escarpment and in the 

 Tennessee Valley; the total linear exposure, if only a single seam is 

 taken into account, is 245 miles, of which 60 miles is workable hard ore. 



Central east Tennessee is the most productive area in the state. 



Underground (slope and adit) mining is carried on almost exclusively. 



"Notes on the Iron Industry" conclude the report. 



V. O. T. 



