Abstract <p>A new analytical method is proposed for the de termination and reporting of ‘acid-reactive silica’ under a fixed set of conditions that can be validated by a single laboratory. Acid-reactive silica exists as fluorosilicic acid during phosphate extraction processes. It is formed when fluoride inherent in the source rock (e.g., fluorapatite, francolite, fluorite) is liberated and reacts with siliceous minerals. To prevent corrosion, contamination with glassware, and volatile analyte losses—which have historically been major obstacles—the method involves acid digestion of the sample in Teflon-sealed cartridges during a microwave heating process, followed by elemental silicon analysis by inductively coupled plasma-optical emission spectroscopy. This method is useful for those in the mineral processing industry, particularly in processing phosphate minerals, where mineral acid is used to extract phosphate and other elements from geological ores. Predictive forecasting and quality control are needed in these industrial processes to control and recover fluorine byproducts, which pose enormous health and environmental concerns. Fluorosilicic acid itself is highly corrosive, but it is precipitated out in subsequent evaporation stages of phosphate production as sodium or potassium salts, thereby effectively making it a corrosion absorber for the holistic process. Due to this unique property, acid-reactive silica represents an invaluable but historically unestablished material property that requires definition.</p>