Laterites are a source of aluminium ore; the ore exists largely in clay minerals and the hydroxides, gibbsite, boehmite, and diaspore, which resembles the composition of bauxite. In Northern Ireland they once provided a major source of iron and aluminium ores. Laterite ores also were the early major source of nickel.
Laterite is a residual material. This is what is left of common silicate rocks if we remove much of silica, alkali, and alkaline earth metals. It is mostly composed of iron, aluminum, titanium, and manganese oxides because these are the least soluble components of the rocks undergoing a type of chemical weathering known as laterization
Composition and properties
Laterites consist mainly of the minerals kaolinite, goethite, hematite, and gibbsite, which form in the course of weathering. Moreover, many laterites contain quartz as a relatively stable, relic mineral from the parent rock. The iron oxides goethite and hematite cause the red-brown color of laterites.
Laterites can be soft and friable as well as firm and physically resistant. Laterite covers usually have a thickness of a few meters, but occasionally they can be much thicker. Their formation is favored by a slight relief that prevents erosion of the surface cover.
Silicate type (or saprolite type) nickel ore formed beneath the limonite zone. It contains generally 1.5-2.5% nickel and consists largely of Mg-depleted serpentine in which nickel is incorporated. In pockets and fissures of the serpentinite rock green garnierite can be present in minor quantities, but with high nickel contents - mostly 20-40%. It is bound in newly formed phyllosilicate minerals. All the nickel in the silicate zone is leached downwards (absolute nickel concentration) from the overlying goethite zone.
You must be logged in to post a comment.
© Copyright 2013-15, All Rights Reserved by Rich Field Minerals