ACCESSORY MINERALS (from the late Latin word "accessorius", which means "additional", "circumstantial" * EN: accessory minerals; DE: okzessorische Minerale; FR: mineraux accessoires; ES: minerales accesorios; RU: акцессорные минералы) are the minerals, which are contained in the rocks in the non-significant quantities (less than 1%).
The accessory minerals of the igneous rocks are of both the early and late magmatic, and autometasomatic (pneumatolytic-hydrothermal) geneses. The accessory minerals in the sedimentary rocks are represented mainly by the clastic, often rolled up grains. The rare metallic accessory minerals acquire the practical importance (especially the (hatchettolites) tantalum niobates) in the certain cases. The typical accessory minerals of the granites are the apatite, zircon, tourmaline, garnet, allanite, titanite, fluorite, topaz, ore ones (magnetite, ilmenite, pyrite), rutile, anatase, monazite, xenolith, cassiterite, thorite, tantalum niobates (fergusonite, samarskite, euxenite, columbite-tantalite, pyrochlore-microlite, and others). During the destruction of the rocks in the crust of the weathering, the accessory minerals are usually preserved and accumulate themselves in the placer deposits, often forming the industrial accumulations.
Most of the accessory minerals concentrate themselves in the heavy fraction (the density is more than 2890 kilograms per cubic metre) during the mineralogical analysis. The accessory minerals are isolated from the rocks mainly by the gravity methods of the benefication. The accessory minerals and their associations are used for the solution of the various geological problems: of the stratigraphic and petrographic correlations (including the correlations of the cross sections of the dumb oil-bearing and coal-bearing depositions), of the determination of the age of the rocks, of the judgment about the sources and routes of the drift of the clastic material (in particular, during the formation of the placer deposits).
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