EARLE, INTERBEDDED IRON ORE DEPOSITS 133 



Field Evidence 



In a small seam of oolitic hematite about eight inches in thickness 

 located at Big Stone Gap, Virginia, the writer discovered what at first 

 appeared to be a small bowlder (Plate XI, fig. 1) entirely surrounded by 

 iron oolites. Upon removing the stone and breaking it, lie found that 

 instead of being an ordinary bowlder, it was an original formation, such 

 as is often present in beds of loose sand that have been penetrated grad- 

 ually by mineral-bearing solutions and consolidated by the well known 

 process of cavernous consolidation, leaving loose sand-filled cavities (Plate 

 XI, fig. 1). The "bowlder" was well filled with practically pure loose 

 quartz sand, with no iron-coated or hardly even iron-stained grains (Plate 

 XI, fig. 2) and was merely the first of several also similarly sand filled. 

 Here we have a local accumulation of sand made up of quartz grains 

 entirely surrounded by iron-coated oolites, yet completely ignored by the 

 iron-charged solutions and not even consolidated. A little farther on in 

 the same seam, another small mass of yellowish white sand was found, 

 which was partly consolidated but had not been penetrated by the solu- 

 tions that coated the surrounding oolites (Plates XII, XIII). 



If we still believe that the iron-bearing solutions were a part of the 

 sea-water, how can we explain two sets of different consolidations, one 

 with iron the other without iron, from the same source and at the same 

 time as the surrounding conditions seem to indicate in this case? Let it 

 be emphasized that these occurrences are situated not at margins of ore 

 seams, but well within a distinct stratum of hematite. 



In Clinton, New York, in a single hand specimen, the writer found 

 oolites coated with iron oxide and other oolites coated with a green min- 

 eral in concentric layers (probably an iron silicate, greenolite) and still 

 a third type of oolite composed of a quartz nucleus, then a ring of iron 

 oxide, then a thicker ring of the green mineral and finally another ring 

 of iron oxide. In a seam in Birmingham, Alabama, a single slide of the 

 Clinton ore shows a calcite-coated oolite and an iron-coated oolite side by 

 side. How would it be possible for the iron-charged sea-wat^r to distin- 

 guish between different grains of the same mineral and coat one with one 

 substance and its neighbor with an entirely different mineral? 



At Niagara gorge, we find the Clinton series of limestones, shales and 

 sandstones, but no evidence of iron-ore seams. This indicates that the 

 iron-bearing marine solutions had suspended operations at this point, and 

 yet had been active as far west as Ohio, Wisconsin and Holt County, 

 Missouri. 



Finally, in applying the sedimentary theory to the fossil-ore beds, we 



