34 GEOLOGICAL SURVEY OF ALABAMA 



highest grades of "rubber mica," acceptably prepared 

 under commercial specifications, are stated to have been 

 marketed at prices ranging from $180.00 to as high as 

 $300.00 per ton. 



COMMERCIAL GRADES AND SPECIFICATIONS. 



As known to the trade and the manufacturer, commer- 

 cial mica is of three general classes designated as run-of- 

 mine, sheet, and scrap. 



Run-of-mine mica ; as the name implies, refers to mica 

 in its crude recovered condition, precisely as it comes 

 from the mine, viz : in rough blocks or masses, with 

 their rock edges adhering to them, and of all sizes and 

 grades; their subsequent sheet values having not been 

 as yet determined or being reliably indicated. 



For this obvious reason, the prices offered and com- 

 monly paid for mine-run block are necessarily low, and 

 do not as a rule represent a fair basis of compensation 

 to the miner, as the skilled manufacturer, accustomed to 

 working up such rough block, is better able to approxi- 

 mate its possibilities than any miner lacking this exper- 

 ience and knowledge. A very large percentage of the 

 domestic mica mined both in the West and in the South, 

 has in the past been disposed of on this basis, with re- 

 sultant disadvantages and discouragement to the miner. 



This condition, requiring only special knowledge and 

 a reasonably small amount of necessary and added mine 

 equipment for its abatement, has had a marked effect 

 in limitation of mine output, many small operations hav- 

 ing been abandoned in consequence of such low prices 

 received which would have been otherwise remunerative. 

 The reverse condition, is one of the causes of uniform 

 success in the India mica field. 



Sheet mica, as known to the trade; is defined and class- 

 ified by its physical preparation and condition, and by its 

 adaptability to its various uses and its value therefor. 



The general trade definition of sheet mica refers to 

 split sheets of approximately one-sixteenth inch in thick- 

 ness, more or less properly trimmed or edged. By far 

 the largest part of the domestic mica marketed, is im- 



