THE IRON SERIES (IN PART). 89 



the masses. They occur associated with the usual clay and shale. 

 Farther west, between the Kentucky and Red rivers, are the 

 other deposits, the principal one of which comes low in the series, 

 just over the Subcarboniferous limestone. 1 



2.01.33. Small quantities of black-band have been found in the 

 Deep River coal beds, in North Carolina, associated with the Tri- 

 assic coals. 2 



A large bed, or series of beds, has recently been reported from 

 Enterprise, Miss., in strata of the Claiborne stage. They run from 

 ten to eighteen feet in thickness and extend for miles. 3 Scattered 

 nodules have been noted at Gay Head, Martha's Vineyard. 4 Car- 

 bonate ores are as yet of no importance in the coal measures of the 

 Mississippi Valley. They have been found associated with the 

 Cretaceous coals of Wyoming and Colorado, and indeed the first 

 pig iron of the latter State was made from them in Boulder 

 County, but they are not an important source of ore. 5 An ex- 

 tended bed of very excellent carbonate has recently been discov- 

 ered with coal near Great Falls, in the Sand Coulee region of 

 Montana. Being near coal, limestone, and other iron ores, it prom- 

 ises to be of considerable importance. 6 



2.01.34. Example 4. Burden Mines, near Hudson, N. Y. 

 Elongated lenticular beds of clay ironstone, passing into sub- 

 crystalline siderite, inclosed conformably between underlying slates^ 

 and overlying calcareous sandstone, of the Hudson River stage. 

 The ore occurs in four "basins," which outcrop along the western 

 slope of a series of moderate hills, just east of the Hudson Riv- 

 er. The hills have been shown by Kimball to be the eastern 

 halves of anticlinal folds now reduced by erosion to easterly dip- 

 ping monoclines. The western half of the ore bodies has been 

 eroded away, leaving an outcrop forty-four feet thick as a maxi- 

 mum, which pinches out along the strike and dip. The basins ex- 



1 P. N. Moore, "On the Hanging Rock District in Kentucky," Ken- 

 tucky Geol. Survey, Vol. I., Part 3. 



2 B. Willis, Tenth Census, Vol. XV., p. 306 ; W. C. Kerr, Geology of 

 North Carolina, 1875, p. 225. 



3 A. F. Brainard, " Spathic Ore at Enterprise, Miss.," M. E., XIV. 146. 



4 W. P. Blake, "Notes on the Occurrence of Siderite at Gay Head, 

 Mass.," M. E., IV. 112. 



5 R. Chauvenet, "Notes on the Iron Resources of Colorado," Ann* 

 Rep. Colo. School of Mines, 1885, 1886 ; Trans. Amer. Inst. Min. Eng.> 

 Colorado meeting, 1889. 



6 O. C. Mortson, Mineral Resources U. S., 1888, p. 34. 



