A sand collection system includes a column of coarse sand within a cylindrical container coaxially mounted to the output end of a furnace conduit through which heated gases containing sublimate will pass. A layer of gas permeable material holds sand in position and an aperture in its center assists in directing gases generally to the center of the sand column. The sand column is spaced away from the furnace a distance such that the temperature differential will cause condensation of the heated gases on the surfaces of the sand particles.