Characterization of Future Florida Phosphate Resources
Florida has two major phosphate deposits: the Bone Valley Formation and the Hawthorn Formation. The high grade, easy-to-process Bone Valley deposit is being depleted rapidly, and the mining industry is moving south/southwest to the Southern Extension of Bone Valley formation and the Hawthorn Formation. FIPR initiated this in-house study in November, 1989 to characterize in considerable detail the mining and beneficiation challenges the industry will face as it proceeds southward. We also anticipated that this study would highlight research directions that FIPR and the industry should take to address these technical problems.
Several phosphate mining companies supplied FIPR with core samples collected from both the upper and lower zone of the Southern Extension. These samples were subjected to the following analyses: chemical properties, mineralogical compositions, beneficiation behaviors, rheology of the matrix, consolidation characteristics of the fine slimes and heavy minerals distribution.
As a general comparison with the Bone Valley deposit, this study showed that these future ore bodies are higher in dolomite, clay and silica (insoluble), but lower in P2O5 and aluminum phosphate content.
DOLOMITE: Although the increased dolomite content in the future deposits has long been recognized, this study has underscored the seriousness of dolomite contamination, particularly in the Lower Zone. While the concentrates do contain over 1% MgO, the pebble fractions analyze up to 6% MgO. Obviously, the traditional washing followed by the “double flotation” will not produce an acceptable product.
LOSS OF PHOSPHATE VALUES IN THE SLIMES: The investigators showed that the potential of P2O5 loss with the -150 mesh fraction (slimes) is still very significant: 20% in the upper matrix zone and 11% in the lower zone.
HEAVY MINERALS: Because the phosphate deposits are associated with small quantities of heavy minerals (rutile-ilmenite, staurolite, sillimanite, zircon, etc.), there arises periodically interest in recovering them economically. Data from this study are not very encouraging: the upper zone would yield only 110 tons of heavy minerals per million tons of matrix, rendering just 4.5 tons of Rutile-Ilmenite, 5.3 tons of Staurolite, and 5.3 tons of Sillimanite in the amine tail.