Garnet, emery and mineral abrasives include mined grains such as pumice, carborundum, natural diamond, tripoli, rouge, staurolite, novaculite, silica and other silicate minerals. They differ in terms of type and shape, grid grade or shot size, material composition, and applications. Typically, mineral abrasives are used in abrasive jet cutting, blasting, blending and intermediate cutting, cleaning and surface preparation, and in applications that require coated abrasives. Mineral abrasives are also used in deburring and deflashing, descaling and stripping, fast cutting and aggressive material removal, grinding and ball milling, peening, polishing and lapping, and tumbling and mass finishing.
Selecting mineral abrasives requires an analysis of type and shape, bulk density, and grit grade or shot size. Choices for type and shape include abrasive grain or grit, crushed or irregular, pebbles or balls, and finishing media or nuggets. Bulk density is a material’s mass per unit area accounting for internal porosity. There are several grit grades and shot sizes for mineral abrasives. Choices include ANSI bonded, ANSI or CAMI coated, FEPA F, FEPA P, JIS, mesh-graded, micron-graded, and SAE. ANSI grading systems are used in the United States, while FEPA grading systems are used in Europe. JIS is an acronym for Japanese Industrial Standard.
Mineral abrasives are made of many different materials. Choices include sodium bicarbonate (baking soda) or calcium carbonate; crocus, rouge, or iron oxide; emery; garnet; and sulfate minerals such as kieserite. Calcium carbonate includes aragonite, calcite, chalk, and limestone. Crocus or rouge is ground into a powder and used in polishing and finishing applications. Emery is a naturally occurring mineral abrasive consisting of aluminum oxide particle in a matrix of iron oxide and other impurities. Garnet is a natural silicate mineral. Mineral abrasives that are made of kieserite are relatively soft and water-soluble.
Types of mineral abrasives include magnetite and iron oxide, olivine, pumice, silica and silicate, staurolite, superabrasives and natural diamond, tripoli, and zircon. Magnetite is a natural iron-oxide material. Olivine abrasives consist of a magnesium iron silicate mineral. Pumice is a silica based volcanic (pyroclastic igneous) rock with a very porous structure. Silica and silicate materials include sand, fused silica, quartz, flint, koalin or clay based materials, cordierite, steatite, forsterite, sillimanite, zircon, porcelain, and fireclay. Staurolite is an aluminum iron silicate mineral. Natural diamond is used for grinding nonferrous metals, ceramics, glass, stone, and building materials. Tripoli is most commonly ground into a powder and used for polishing or in finishing compounds. Garnet and mineral abrasives such as tripoli are also available.