PHOSPHORUS MINERALOGY OF THE JAMAICA BAUXITE ORES
The Jamaican bauxite ores contain the highest phosphorus amounts of any bauxite ores in the world, and samples examined for this study contained up to 32% P2O5. Because apatite was thought by some to contain much of the phosphorus in Jamaican bauxites, a cathodoluminescence (CL) microscopy was initiated to examine the character of the phosphorus-bearing grains. Apatite and collophane commonly exhibit distinct CL in other ores and rocks including sedimentary iron ores. Those Jamaican bauxite ores with the highest P2O5 were found to contain phosphorus largely in 200-500µm crandallite fecal pellets. Additional phosphorus occurs in phosphatic collophane bones. These areas of bauxite probably served as roosting areas for sea birds like cormorants that had feasted nearby on anchovy and other fish and subsequently contributed the fish bones to the underlying bauxite. Bauxite ores with lower phosphorus contain only bone fragments. In bauxite ores with the least phosphorus, SEM-EDS analyses indicate that phosphorous is entirely present as rare earth (Ce, Nd, and Dy) phosphates.
Reflected light and SEM-EDS study of opaque grains in a black sand concentrate at Blue Hole spring, speculated to be derived from bauxite protore by underground drainage, identified hematite, martite, titaniferous magnetite, titaniferous hematite with abundant especially well-developed exsolution ilmenite, and ilmenite. The recognition that titanium iron oxides also occur in the bauxite ores suggests that the black sands at Blue Hole were derived from the bauxite protores and that they provided an alluvial addition to those protores.