Abstract: 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.degree. C. to about 1,000.degree. 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.

Abstract: An abrasives formulation is provided for abrasive waterjet processes. The abrasives include a first particulate component which is a high-density, high-hardness crystalline material such as specular hematite. A second particulate component can optionally be combined with the first component and is a medium-density, medium-hardness cryptocrystalline material such as copper slag. An optional third particulate component is any of various ultra-hard materials such as aluminum oxide, boron carbide or silicon carbide. The first component can be used for cutting glass, stone and other brittle materials. The first and second components in combination are used for cutting ductile materials, with the third component being added when hard and/thick metals or ceramics are to be cut. Particles sizes are typically within the range of No. 20 to No. 220 U.S. Standard Sieve.