Fluorite equilibria in thermal springs of the Snake River Basin, Idaho

Some thermal water sources of the Snake River basin, Idaho, are near saturation with respect to fluorite. That mineral was identified by X-ray diffraction in precipitates induced in three water samples by adding sodium fluoride. The derived solubility product (K_S0) for zero ionic strength was close to that calculated from Latimer's thermodynamic data (10^{-9.7 7}). The relative ease of precipitation of fluorite from these water samples indicates that equilibrium with respect to fluorite may occur in some ground-water systems.