The contribution of individual grain size fractions (2000-500, 500-250, 250-63, 63-2 and < 2 μm) to bulk soil surface area and reactivity is discussed with reference to mineralogical and oxalate and dithionite extractions data. The 63-2 μm fraction contributed up to 56% and 67% of bulk soil volume and BET surface area, respectively. Consideration of these observations and the mineralogy of this fraction suggest that the 63-2 μm fraction may be the most influential for the release of elements via mineral dissolution in the bulk soil. © 2011 Elsevier Ltd.