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The sand reserve came from a old stream bed, that had a 20 to 30 ft thick sand deposit in it. It was sampled and the lab testing revealed that there was less than 0.03% iron, and a few other metals (TiO2, Al2O3, MgO). The length of the deposit was over a mile, so sufficient reserves were in place to justify a mining operation. The site was permitted and the sand was excavated and processed. Initially, the sand was sent to attrition scrubbers at around 50% solids, to remove any clay material (Al2O3) that is typically found in stream sediment. The attrited sand was then sent to a agitated holding/conditioning tank, where flotation reagents and water were added. A 30% solids slurry was then sent to a series of froth flotation cells where the silica dioxide was separated and the contaminating metals were removed, giving a 99.8% pure SiO2 product that glass manufacturers need to manufacture high quality glass. The concentrate from this flotation process was the iron and other heavy metals, and the tailings was the high purity sand. The sand was de-watered on a series of cyclones, depositing their wet, sand in a stockpile to dry further in the hot desert sun. Sand from the stockpile was reclaimed by a bucket loader, conveyer and feeders and sent to a rotary dryer to further dewater and the final product was loaded into rail cars and sent to the glass plant customer. Being abrasive, the equipment was rubber lined and ceramic lined to prevent wear and further iron contamination. Information provided by Charles Kubach, Mining and Mineral Processing Engineer |
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