Correlation between particle size and surface area for chlorite and K-feldspar

The specific surface area as determined by BET analysis is often used for scaling mineral surface reaction capacities and rates between particles of different sizes as found in nature. Generally, an inverse proportionality between BET area and particle size is assumed, based on geometry. However, macroscopic laboratory studies of mineral surface reactions generally employ crushed material that may have been mechanically disturbed, potentially leading to an artificial increase in the specific surface area, and a change in the apparent surface reactivity. In this study, we determine the BET area for natural K-feldspar and chlorite samples from Sweden as function of particle size in a first step towards relating the surface reactivity for these minerals to grain size.