The Nature of Phosphorous-bearing Mineral Grains in the Birmingham, Alabama Sedimentary Iron Ores and an Assessment of Their Potential Liberation by Beneficiation

Microscopic examination of selected, representative, unweathered samples of Birmingham, Alabama, Silurian, sedimentary iron ores has fully revealed the nature of the phosphorous-bearing mineral grains. The grains are composed of carbonate-fluorapatite (collophane), range in size from 1 μm to 2.25 mm, and exhibit varied types of intergrowth with hematite. Modal analyses conducted under cathodoluminescence have provided quantitative data on the abundance of each of 15 types of phosphorous-bearing mineral grains and made it possible to assess the potential phosphorous liberation from four types of iron ore. The results indicate that 27% of the total phosphorous contained in the iron ores in the western part of the Birmingham district can be expected to be liberated by fine grinding; 60% for ores in the eastern part of the district.