Chemical precipitation in a porous medium lowers both the local porosity and permeability. This paper compares several models relating the reduction in porosity and permeability to laboratory data obtained for chemical precipitation in Berea sandstone. Traditional capillary tube models for the porous medium, including the Carman-Kozeny model, significantly underpredict the reduction in permeability for a given reduction in porosity. This failure arises because those models fail to account for the effect of pore geometry, e.g., narrow pore throats, on permeability. A new model based on sinusoidal pores is developed that accounts for this geometry. Empirical constants for exponential and power law models are also provided.