The porosity/cement ratio is defined as the ratio between porosity and the volumetric cement content (volume of cement over the total volume) and it is often adjusted by an exponent (ξ) to the volumetric cement content ([Formula: see text]), which seems to depend on the type of soil. This ratio is very useful to analyse artificially cemented soils and it depends on easily calculated moulding properties. Although there are already some results regarding the correlation of this ratio with the mechanical behaviour of different soils, a theory explaining the variation of the exponent ξ has yet to be established. In this work, the influence of grain size and mineralogy on ξ was pursued, considering them to be the most important factors. For that purpose, a soil was divided into three different fractions, whose grain size distribution and mineralogy were known, and the exponents obtained correlating the ratio with the maximum shear modulus or the unconfined compression strength were compared. The results show that the grain size distribution explains part of the ξ variation, but mineralogy and particle shape seem to have the most decisive influence. This was even more evident when comparing two uniform sands.