Metallurgical grade alumina (MGA), also known as smelter grade alumina (SGA), is a refined form of aluminium oxide (Al₂O₃) produced from bauxite ore through the Bayer process, specifically intended for use as the feedstock in aluminium smelting via the Hall-Héroult electrolytic process. It is distinguished from chemical grade alumina, which is used in ceramics, abrasives, and specialty chemicals. Metallurgical grade alumina typically contains 99.5% or more Al₂O₃ on a dry basis, with tightly controlled levels of impurities such as silica, iron oxide, sodium oxide, calcium oxide, and moisture, all of which can adversely affect smelting performance, current efficiency, and the quality of primary aluminium produced. The physical properties of MGA — including particle size distribution, angle of repose, specific surface area, and alpha-alumina content — are critical to its flowability through automated alumina feeding systems in modern smelting pots. Bauxite mining operations are the origin point of MGA production, and the quality of the bauxite ore (particularly its available alumina content, reactive silica levels, and moisture) directly influences the efficiency of Bayer process refineries and the quality of the metallurgical grade alumina they produce. Global demand for MGA is driven primarily by the aluminium smelting industry.
