that this micro porosity is the result of the voids created as large sulfate or sulfite ions are replaced by sulfide ions within a solid particulate structure by means of the high temperature reduction process inherent in the process of the present invention only metal sulfides having a melting temperature higher than the 900 degrees c to 1100 degrees c chemical reduction reaction temperature will retain the unique micro porous structure inherent in the product of the present invention thus strontium sulfide an alkaline earth metal sulfide with a melting point above 2000 degrees c retains the desired micro porous structure calcium sulfide another alkaline earth metal sulfide has also been found to retain the micro porous structure integral to the product of the present invention iron ii sulfide with a melting point of about 1171 degrees c will retain the micro porous structure inherent in the products of the present invention unless impurities are present which act as u201c mineralizers u201d that is which act to reduce the temperature at which a liquid phase appears to facilitate the process of high temperature reduction it is highly desirable that the metal sulfates and metal sulfites subjected to the process of the present invention also remain solids at the high temperatures required to reduce sulfate and sulfite ions to sulfide ions using the reducing agents taught herein in general sulfates sulfites and sulfides of most polyvalent metals have very high melting temperatures and are suitable for the process of the present invention thermal reduction is preferably accomplished in a high temperature countercurrent rotary kiln utilizing as the reductant coal.