Equilibrium in the system granite-SnO2-H2O-HCl was modeled experimenta
lly and on a computer. Three main factors were shown to control the fo
rmation of commercial tin concentrations: the chemical properties of a
queous fluid (HCl content and pH), the dynamics of fluid filtration th
rough rock (ensuring that the weight ratio of reacting rock and fluid
is above 0.1), and the presence of accessory cassiterite in the rock.