Applications of Ore Microscopy to Beneficiation Problems Involving Phosphorus



Large collophane (Col; light blue) grains (faecal pellets) in Alsase-Lorraine limonitic iron ores, France. Calcitic fossils (Cal; bright yellow), goethite (Goe; black), and very fine-grained collophane constitute the rest of the slide. The presence of abundant collophane results in very high contents (0.9% P2O5) of deleterious phosphorus to be present in these iron ores. Cathodoluminescence microscopy, low magnfication.



Numerous small grains of apatite (Ap; bright bluish white) in quartz (Qz; dull brown)-rich hematitic (Hm; black) iron ore. Saivo mine, Kiruna District, Sweden. The intergrowth of apatite with hematite results in locked apatite-hematite grains and high contents of deleterious phosphorus in the iron concentrates from this ore. Cathodoluminescence microscopy, low magnification.



Apatite (Ap; light blue) grains within fluorite (Fl; deep blue) ores at the Okorusu fluorspar mine, north-central Nambia. The intergrowth between apatite and fluorite results in high contents of deleterious phosphate in the fluorite concentrates. Other mineral inclusions in fluorite include potash feldspar (red), calcite (yellow), and magnetite (black). The fluorite ores are genetically associated with a carbonatite intrusion, and the calcite is derived from that source. In most rocks potash feldspar exhibits blue cathodoluminescence (CL), but due to the oxidation of trace amounts of ferrous iron in the feldspar during introduction of the oxidizing environment of the carbonatite the iron is oxidized to ferric iron which acts as a activator for red CL. Cathodoluminescence microscopy, low magnification.



Apatite (Ap; bright yellow) grains in magnetite iron ore from Benson Mines, Adirondack Mountains, New York. Part of the apatite grains that are intergrown with magnetite are pulled into the magnetic concentrate resulting in the presence of phosphate, a deleterious constituent in iron concentrates. Other minerals present in the iron ores include potash feldspar (Fd; deep blue), magnetite (Mt; black), and biotite (Bio; black; platy). Cathodoluminescence microscopy, low magnification.



Abundant free dolomite particles (D; bright yellow) grains in phosphate concentrate made from phosphate concentrate from the South Florida Phosphate District. The collophane (C) grains cathodoluminesce a variety of colors, including medium dark bluish grey, light blue, white, and pink, due to the presence of various amounts of trace element activators. The grains are embedded in plastic in a polished section. Cathodoluminescence microscopy, low magnification (16X in original photomicrograph).