ABRASIVENESS of the rocks
ABRASIVENESS of the rocks (EN: rocks' abrasivity, abrasiveness; DE: Schleifscharfe von Gesteinen; FR: abrasivite des roches; ES: abrasividad de las rocas; RU: абразивность горных пород) is the ability of the rocks to wear down the solid objects, which are in the contact with them (the parts of the mining machinery, tools, etc.).
Is determined mainly by the strength, size and shape of the mineral grains, composing the rock. The abrasiveness is evaluated by the degree of the wear of the pins, rods, metal rings, that rub against the surface of the rocks at the time of the drilling or cutting, as well as by the degree of the abrasion of the rocks by the abrasive materials.
The indicator of the abrasiveness (according to the method by L.I.Baron and A.B.Kuznetsov) is defined as the total loss of the mass (in milligrams) of the rotating (at the 400 revolutions per minute) standard unhardened steel rod by the abrasion of its end face, which is pressed against the rock, under the axial load of the 150 newtons during the test period (10 minutes). For example, the indicator of the abrasiveness is the 400-500 milligrams for the marble, 800-900 milligrams for the limestone, 1000-2000 milligrams for the granite, 2100-2500 milligrams for the quartzite.
For the rocks with the low abrasiveness (less than 5 milligrams), such as coal, the indicator of the abrasiveness is defined by the abrasion of the standard sample (with the constant pressure at the contact) on the crushed sample of the rock. The rocks are divided into the 8 classes (according to L.I.Baron and A.B.Kuznetsov) according to their abrasiveness.
The rocks which contain corundum, such as the porphyrite, diorite, granite, are the most abrasive. The abrasiveness affects the efficiency of the drilling, cutting, chipping, scooping the rocks.
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