Industrial Minerals - Mica Process Development

For the past several years, USBM has conducted laboratory and continuous process development work on the weathered mica pegmatites ores of Alabama, Georgia, and North Carolina to determine the feasibility of recovering commercial-grade mica concentrates by flotation. The research has resulted in the development of two processes for flotation of mica: 1) an acid-cationic method for recovery of coarse mica and 2) an alkaline-anionic-cationic method for recovery of fine mica. The research indicated that the two processes may be effectively utilized separately or in combination for flotation of mica from weathered pegmatite ores. This report summarizes the process development work, and demonstrates the feasibility of producing commercial-grade concentrates with a high recovery of the contained mica. Mica mining in the United States is confined largely to pegmatites and schists in a few well-defined areas. The largest region extends from central Virginia southward through western North and South Carolina, northern Georgia, and east-central Alabama.'" Whereas in western North Carolina, these pegmatite dikes are weathered to only a shallow depth, they are deeply weathered in the Carolina Piedmont and in Georgia and Alabama. Particularly in Georgia and Alabama, mica is found in the decomposed slates and schists adjacent to the pegmatites, and in deeply weathered granites. Most flake mica is obtained as the major marketable product by crushing and milling pegmatites4 To a lesser extent, mica is produced as a byproduct of feldspar" and spodumene. Past research by U.S. Bureau of Mines (USBM) has developed two methods for mica flotation. One method utilizes acid-cationic flotation for recovery of mica.' This method requires thorough desliming of the ore with consequent fine mica losses. The other utilizes an alkaline-anionic-cationic process for recovering fine-size mica from pegmatite ores after desliming sufficiently to remove clay materials but not so drastically as to remove the fine mica.8-18 The latter process has also been successfully applied to a micaceous schist ore from California.' This report summarizes the results of these research studies. Both of the flotation processes developed by USBM have been adopted by the mica industry and are being commercially utilized separately and in combination for flotation of mica from weathered pegmatite ores. Description of Ores The weathered mica pegmatite ores used in the investigations were obtained from commercial mica operations in Alabama, Georgia, and North Carolina. The