Thermal feedback has the potential to enrich immersive interaction, yet its role in material discrimination remains underexplored. We designed and evaluated a conductivity model that simulates transient heating and cooling profiles based on material properties of an object. Thirty-eight participants used a Meta Quest 3 headset and WEART TouchDIVER Pro gloves to classify virtual blocks (metal, glass, wood) under three conditions: visual-thermal congruence, thermal-only, and visual-thermal incongruence. Although the results show accuracy decreased when congruence decreased, the objects were rated consistently following their material conductivity properties (Metal > Glass > Wood), supporting the validity of the conductivity model. Haptic Experience (HX) ratings of realism, involvement, and harmony remained stable across tasks, while sorting difficulty was lowest under congruent and highest under incongruent visuals. Physiological baselines did affect performance. Our findings demonstrate that conductivity-based thermal rendering enables perceptually reliable material differences in VR, informing design and application of thermal haptics.