36 GEOLOGICAL SURVEY OF ALABAMA 



domestic mica (or double the quantity of uncut mica), 

 to yield 1000 acceptable condenser films. By careful se- 

 lection it has been possible to obtain a pound of cut films 

 from 5 to 6 pounds of domestic uncut sheet mica. 



Phonograph or diaphragm mica is also a variety of 

 very high grade. It must be free from all imperfections, 

 such as rulings, cracks, and inclusions of other minerals, 

 must split well and evenly, must be clear and transparent, 

 and must also be flat, this last feature being an essential 

 character of diaphragm mica. Mica for lamp chimneys 

 and canopies must be clear, split easily, and be extremely 

 flexible. Very little domestic mica is so used. 



For stove glazing, a hard rigid mica is preferred, as 

 nearly clear as possible. The greenish North Carolina 

 mica ^receives the preference for this purpose. 



Splittings, commercially speaking, are very thin sheets, 

 approximately one thousandth of an inch in thickness, 

 may be irregular in shape and size, and may contain 

 some flaws or imperfections. They are altogether pre- 

 pared by hand, most of the large India preparation of 

 splittings being made by women and children, a long 

 thumb nail being there largely used in preference to a 

 knife for this purpose. From 2 to 4 pounds per day of 

 splittings represents an average production. A variable 

 amount of domestic splittings accumulates necessarily in 

 the working up of mine-run mica and in the general hand- 

 ling of cut and uncut sheet into specific forms. 



The otherwise waste product of the mine in the form 

 of mica recovered having no sheet value, and the waste 

 resulting from the cutting, trimming and preparation of 

 sheet mica, etc., collectively classes as scrap, which as 

 sold and utilized for grinding may have, and usually con- 

 tains inclusions of various kinds, mainly quartz and 

 feldspar. 



ASSOCIATIONS. 



The useful associated minerals of the pegmatites in Ala- 

 bama, of possible value as by-products, recovered neces- 

 sarily in the ordinary course of mica mining, are kaolin, 

 feldspar, and quartz ; stated in the order of their ordinary 

 commercial importance. 



