What is emery? What are the properties of emery mineral? Information about emery and uses.
Emery; is a composite mineral that consists mainly of corundum (aluminum oxide) and magnetite (iron oxide). An important abrasive in the early days of industrial development, emery serves a minor industrial role today. Adequate for the nonprecision grinding and polishing of hard materials such as metal and glass, it is available as a coating on cloth or paper and in a loose granular form mixed with oil or water. The loose form is also used in nonskid, long-wearing stair treads, adhesive strips on ramps, and floor materials.
Mined in Greece, Turkey, and the United States, emery is processed to control its corundum content and grain characteristics. These factors largely determine how it is used. Greek emery has the highest corundum content and is suited to faster abrading, whereas other forms of emery, containing less corundum, are better suited to polishing. Coated emery products are graded by grain size but may be designated as fine, medium, or coarse, according to the kind of work to be done. A 220 grit size, in which the grains are about 70 microns (0.0027 inch) wide, is “fine,” and a 50 grit size of about 420 microns (0.016 inch) is “coarse.”
Because of its nonuniform character, emery has an unpredictable abrading performance, even though the hardness of natural corundum is between 8.5 and 9 on Mohs’ scale. Compared to the uniform properties and dependable performance of synthetically manufactured aluminum oxide and silicon carbide abrasives, emery does not compete favorably in industrial grinding and polishing operations.