THE MINERAL EVANSITE 227 



north fork of Yellow Leaf Creek through Double Mountain) covers a dis- 

 tance of about fifteen miles. 



The Martin coal seam in which the Alabama evansite is found as an 

 unevenly disti'ibuted coating on the bedding and in the joints and cracks, 

 is unique in being at once the thickest and probably, as to quality, the most 

 inferior coal bed in the South. The section herewith presented not only 

 gives the thickness of this mammoth coal bed but shows also the strati- 

 graphic points in the seam where the evansite is found best developed. 



Section. 



Ft. In. 



Clay and soft pink colored shales - 2 



Thin, soft and reddish sandstones 2 



Yellowish gray sandstone and clay 2 



Coal with evansite coating below 7 1 



Blue clay parting — apparently widening down the. dip 2 



Coal with evansite coating at top and more or less throughout 8 6 



Under clay — dark and thick 



The unusual thickness of coal as shown by the section above appears 

 to be due to a sharp plication accompanied near the outcrop with faulting 

 and the normal thickness may therefore be nearer 8 than 16 feet as now 

 appears to be the case. However, as the coal here was found to be of such 

 inferior quality it was unnecessary to carry the work further in order to 

 determine exact structural relationships. The analysis which follows 

 gives the chemical composition and may serve also as a partial clue to the 

 genesis of the evansite. The results obtained from other analyses made on 

 samples taken foot by foot show very little variation from the percentages 

 given in the bulk sample representing the entire bed, and hence the analy- 

 sis above referred to not only represents an average composition but prac- 

 tically also the quality of the coal in any foot of the bed that may be selected. 

 In taking the various samples, which was done under great difficulty 

 because of the rapid inflow of water into the shaft, it was noted that the 

 coal had a dominant dull, black, dead and lusterless look but here and there 

 possessed a pavonine glint of a more or less greasy and greenish tone, which, 

 had it been a limonite, would have suggested at once the presence of phos- 

 phorus. However, this is seen so often in coal in which phosphorus is 

 entirely absent that but for its actual presence disseminated here through 

 the coal as one of the main constituents of evansite — it would have no real 

 significance. Phosphatic matter supplied by the bones and excreta of 

 organisms, together with the introduction of the mud at the time the car- 

 bonaceous material was accumulating, plus the aliimina, ferric oxide and 



