Garnet (7.5-8 on Mohs Hardness Scale) is harder than Glass Abrasive (5-6 on Mohs), but not as aggressive as Aluminum Oxide (9). Therefore, white metal finishes can easily be achieved on steel without embedment or excessive metal removal (as can happen with AO), while being hard enough to perform effectively even on harder metals and coatings. We recommend Garnet over Glass Abrasive when it is necessary to remove very hard and deeply pitted rust, mill scale, other tough coatings, when profiling hardened steel, and definitely when water-jet cutting. Leaves a smoother surface profile than sand or slag media. Fine, fast-cutting media. Excellent for glass etching on finer projects. Durable/effectively recycles through blasting cycle many times. Mohs Hardness Scale: 7.5-8; Specific Gravity: 4.0-4.1; MIL — A-22262B; CARB Certified; NSF Certified to ANSI/NSF61; Made of Natural Almandine Garnet; Contails NO HEAVY METALS; Crystalline Silica content is less than 0.5%. MINED, PROCESSED, AND PACKAGED IN THE U.S.A.