A New Method for Rapid Brucite Quantification Using Thermogravimetric Analysis

Brucite [Mg(OH)2] is a trace mineral found in ultramafic deposits that readily reacts to trap atmospheric CO2. Identifying and quantifying brucite content is an essential first step in determining the carbon sequestration capacity of many ultramafic mine tailings. Quantification via X-ray diffraction (XRD) has proven problematic in the past due to peak overlap issues between brucite and chlorite. Quantitative thermogravimetric analysis (TGA) methods have been used previously; however, they typically require multiple long (>10 h) analyses. Here, we demonstrate a method for rapid quantification of brucite content via TGA. Using an exponential model to fit and ignore mass loss from other minerals, brucite can be consistently detected and quantified at abundances of as low as 0.3 wt.%, a detection limit that is superior to XRD. Relative errors are as low as 3.4% for brucite abundances greater than 2 wt.%.