Two grades of sands are commonly used in glass making: a white, low iron oxide sand for flint glass (also known as flint grade glass sand), and a higher iron oxide amber sand for coloured glass and flat glass. Although amber sand has a higher iron oxide content, both products are required to have specified and consistent chemical composition and particle size distribution. Flint grade glass sand is normally required to have an iron oxide content of < 0.03% while an amber glass specification might call for an Fe2O3 content of around 0.15%.
Bulk samples of premium grade (white) sandstone, collected from exploration drill holes within the SCM friable sandstone resource, have been tested by a commercial laboratory in Melbourne for full chemical analyses. Iron levels (Fe2O3) fell into the 0.03% industry specification. Alumina levels were marginally higher than the accepted normal levels. It is reasonably predictable that iron levels would be further reduced by attritioning during processing and washing of the sands. Chrome at 0.0004% is well below the 0.0006% industry standard.
Based on these results, it demonstrates the suitability of using premium grade friable sandstone as feedstock for both flint and amber glass. Size fractionation will be achieved through a series of parallel hydro-cyclones.
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