Answer
Consider 1.0 kg of granite. Calculate the temperature change in one year. The heat transfer is 0.03 J.
$$Q = cm \Delta T$$
$$0.03 J = \frac{800 J}{kg \cdot ^{\circ}C}(1 kg)(\Delta T)$$
$$\Delta T = 0.0000375 C^{\circ}$$
The number of years to go up by 500 degrees is $\frac{500 C^{\circ}}{0.0000375 C^{\circ}/year} = 13.3 \; million \; years$.
