GLASS SAND POTENTIAL OF THE PINEHURST FORMATION, RICHMOND COUNTY, NORTH CAROLINA: MINERAL IDENTIFICATION AND PROCESSING

Split-spoon samples of six drill cores 9 to 18 m deep from the Pinehurst formation, Richmond County, North Carolina, were evaluated for glass sand raw material potential. The Pinehurst Formation, as mapped on the 1985 Geologic Map of North Carolina, covers approximately 120,660 acres, or approximately 0.38% of the state in Richmond, Scotland, Moore, and Hoke counties. Commercial glass sand has been produced from another site from the Pinehurst Formation. Minerals were identified using microscopy and powder X-ray diffraction. The trace heavy minerals found in the raw material included schorl (tourmaline), rutile, and zircon. Less abundant trace minerals were goethite, hematite, muscovite, kaolinite, and chromite. Several physical separation processes were evaluated to make a product suitable for glass application. These included attrition scrubbing, sizing, flotation, heavy-liquid separation, and magnetic separation to remove impurities such as iron, titanium, mica, organic matter, feldspar, and trace elements. The glass sand product after attrition scrubbing, sizing, and magnetic separation contained 0.13-0.16% Al₂O₃, 0.02 - 0.04% Fe₂O₃, < 0.01 - 0.02% TiO₂ and traces of other minor elements. Further reduction of impurities will be obtained from separation processes that include flotation. This product is well within the specifications for typical glass sand and is suitable for many glass sand applications. Subsequent work will produce a bulk sample through a continuous pilot plant operation. The pilot plant operation will also generate design data for a commercial plant.