ALABAMA MICA DEPOSITS 13 



trict to fourth place, (after India, the United States, and 

 Canada), in production of sheet mica, and making it 

 third in importance, on the basis of the actual value of 

 world output of sheet muscovite. 



In the Union of South Africa, practically all the known 

 deposits of value are in the Transvaal, existing opera- 

 tions having been confined to three localities. The mica 

 recovered has been commonly of large size but of some- 

 what defective structure in the crystals, limiting the 

 amounts of recoverable sheet in these larger books. The 

 brownish muscovite of the Leydsdorp* field, however has 

 proved to be equal to the best grades of Indian and Cana- 

 dian mica for electrical purposes. In recent Memoir No. 

 13 of the Geological Survey, Department of Mines and 

 Industries, Union of South Africa, a mica belt is reported 

 of some 300 square miles in area, which has been worked 

 to a considerable extent since 1909, but until the opening 

 of the Selati Railway in 1912, which now crosses the 

 mica field, the nearest railway shipping point has been 

 120 miles distant. In reviewing the operations of six 

 operating companies, the finding of some exceptionally 

 large blocks is noted, but as a whole the merchantable 

 mica recovered, although of favorable grade, is stated to 

 have been mainly in comparatively small sizes. Some 

 idea of mining conditions and cost of recovery may be 

 gained from the stated fact in Memoir No. 13, that to 

 procure one ton of mica, trimmed and in marketable 

 condition, it has here been found necessary to mine from 

 850 to 1700 tons of rock. Also the great waste in this field, 

 suitable for grinding purposes, has been practically un- 

 used. During the period 1909 to 1917, the Transvaal 

 output, averaged annually only about four tons. Recent 

 export figures, although not as yet available, would prob- 

 ably not show this field of much relative importance. 



Only small production is noted from the Island of 

 Madagascar, the last annual output reported in 1913 be- 

 ing 6 tons, although something like 125 tons per year is 

 stated to be a possible expectancy. The mica mined con- 

 sists of both muscovite and phlogopite. Only a small 

 proportion of the muscovite is clear sheet, the greater 

 part of it being discolored or spotted. With the excep- 



