Iron based roofing granules and method of coloring same

摘要

Method of preparing colored roofing granules (18) from granulated mineral-containing matter having an elemental iron content of about 15% to about 70% is disclosed. The method comprises heating the granules (18) to a temperature of from about 450 DEG C. to about 1,000 DEG C. and maintaining the temperature for a period of time sufficient to effect a color change in the granules. The resulting oxidized granules are permanently colored and will not fade in use.