We modeled the thermodynamic evolution of the venusian crust in the presence of an atmosphere and paleo-ocean during a potential climate transition to its present uninhabitable state. We show that the present-day atmospheric composition of Venus is reproduced by the interaction between a paleo-ocean and crust during a runaway greenhouse. The evolution of oxygen fugacity with increasing surface temperatures converges with the present-day value (10-20 bar) at current temperatures (400-500°C). Other atmospheric species (CO, CH4, H2S, SO2) show varying behavior depending on RedOx, but are consistent with increasing oxygen fugacity. Low-pressure conditions result in the genesis of unique mineral parageneses, including tremolite and zeolites, that could survive on Venus over geological timescales and are indicative of stable liquid water in the past if detected by future missions. Therefore, the resulting venusian mineralogy in our models could be markers of past habitable conditions that were altered by a significant greenhouse effect.