98 JOUKJSTAL OF THE MiTCHELL SoCIETY \_AugUSt 



Up to this time there was no use made of the scrap mica nor 

 for the small sheets, and it was not until about 1890 that a 

 demand arose for the small sheets and punched mlica for elec- 

 trical apparatus. This demand for the waste mica together 

 with the duty caused a revival of the mica industry of the 

 South. A use was also found for scrap mica, to be used in manu- 

 facture of axle grease, wall paper, etc., which added greatly to 

 the income of mica mining and greatly increased the produc- 

 tion of the Southern mines. There has always been a strong 

 competition between the Southern and the imported mica. The 

 Southern mica was always able to easily compete with the for- 

 eign when there was a large demand for it for stoves, but with 

 the smaller demand for this purpose and the much larger de- 

 mand for use in electrical purposes, for which the foreign mica 

 gives equal satisfaction with the Southern mica the competition 

 has been greater, and often to the disadvantage of the Southern 

 mica. 



OCCUEKENCE. 



The muscovite represents the most conamon mica and is 

 very widely distributed, being a component of many of the 

 crystalline and sedimentary rocks. In many of these it occurs 

 in but small scales or crystals which have no commercial value. 

 When, however, it occurs in blocks or masses which can be 

 split into sheets an inch or more in diameter, it has a commer- 

 cial value which increases with the size of the cut sheets, and 

 these vary from 1 by 1 to 8 by 10 inches. These commercial 

 ■deposits of mica are found for the most part in pegmatitic dikes 

 or veins, which occur as intrusives in granite and in hornblende 

 and mica gneisses and schists, and have been mined in Virginia, 

 Worth Carolina, South Carolina, Georgia and Alabama. These 

 dikes or veins vary in thickness from a few inches to several 

 hundred feet and are often very irregular, having arms or ap- 

 ophyses branching off from them and extending out into the 

 country rock in many directions. Sometimes these dikes are 

 parallel to the bedding or schistosity of the gneiss or schist, and 

 then again they break across it at varying angles. Both of 

 these phenomena are often observed in the same dike. The 



