Cutting of laterite brickstones, Angadipuram, India

Laterite is a surface formation in tropical areas which is enriched in iron and aluminium and develops by intensive and long lasting weathering of the underlying parent rock. Nearly all kinds of rocks can be deeply decomposed by the action of high rainfall and elevated temperatures. The percolating rain water causes dissolution of primary rock minerals and decrease of easily soluble elements as sodium, potassium, calcium, magnesium and silicon. This gives rise to a residual concentration of more insoluble elements predominantly iron and aluminium. Image File history File linksMetadata Download high resolution version (968x1492, 1434 KB) Summary | Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Laterite Metadata This file contains additional information, probably added from the digital camera or scanner used... Image File history File linksMetadata Download high resolution version (968x1492, 1434 KB) Summary | Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Laterite Metadata This file contains additional information, probably added from the digital camera or scanner used... Parent rock refers to the original rock from which something else was formed. ...

Laterites consist mainly of the minerals kaolinite, goethite, hematite and gibbsite which form in the course of weathering. Moreover, many laterites contain quartz as relatively stable relic mineral from the parent rock. The iron oxides goethite and hematite cause the red-brown color of laterites. Kaolin Kaolinite (Aluminium Silicate Hydroxide) Kaolinite is a clay mineral with the chemical composition Al2Si2O5(OH)4. ... Goethite is a iron bearing oxide mineral found in soil and other low temperature enviroments. ... Hematite (AE) or haematite (BE) is the mineral form of Iron (III) oxide, (Fe2O3), one of several iron oxides. ... Gibbsite, Al(OH)3, is an important ore of aluminium and is one of three minerals that make up the rock bauxite. ... Quartz is amongst one of the most common minerals in the Earths continental crust. ...

Laterite covers have mostly a thickness of a few meters but occasionally they can be much thicker. Their formation is favoured by a slight relief which prevents erosion of the surface cover. Laterites occurring in non-tropical areas are products of former geological epochs. Lateritic soils form the uppermost part of the laterite cover; in soil science specific names (oxisol, latosol, ferallitic soil) are given for them. Oxisols are an order in USA soil taxonomy, best known for their occurrence in tropical rain forest, 15-25 degrees north and south of the Equator. ...

In geosciences only those weathering products are defined as laterite, which are geochemically - mineralogically most strongly altered. They must be distinguished from less altered saprolite which has often a similar appearance and is also very widespread in tropical areas. Both formations can be classified as residual rocks. Saprolite is a soft, clay-rich, decomposed rock formed in place by chemical weathering of igneous or metamorphic rock. ...

Laterites can be as well soft and friable as firm and physically resistant. Indurated varieties are sometimes cut in blocs and used as brickstones for house-building. The term laterite which is derived from the Latin word later = brickstone is given because of this usage. Most of the Khmer temples at Angkor are built with laterite and have survived for over 1000 years. Hardened laterite varieties are also applied for the construction of simple roads (laterite pists). Nowadays solid lateritic gravel is readily put in aquaria where it favors the growth of tropical plants. Angkor was the site of a series of capital cities of the Khmer empire for much of the period from the 9th century to the 15th century CE. Their ruins (13°24N, 103°51E) are located amid forests and farmland to the north of the Great Lake (Tonle...

Lateritization is economically most important for the formation of lateritic ore deposits. Bauxite which is an aluminium-rich laterite variety can form from various parent rocks if the drainage is most intensive thus leading to a very strong leaching of silica and equivalent enrichment of aluminium hydroxides above all gibbsite. Iron ore (Banded iron formation) Manganese ore Lead ore Gold ore An ore is a volume of rock containing components or minerals in a mode of occurrence which renders it valuable for mining. ... Bauxite with penny Bauxite (pebbly) Bauxite is a naturally occurring, heterogeneous material composed primarily of one or more aluminium hydroxide minerals, plus various mixtures of silica, iron oxide, titania, aluminium silicates, and other impurities in minor or trace amounts. ...

Lateritization of ultramafic igneous rocks (serpentinite, dunite,peridotite containing about 0,2 - 0,3% Ni) often results in a considerable nickel concentration. Two kinds of lateritic nickel ore have to be distinguished: A very iron-rich nickel limonite or nickel oxide ore at the surface contains 1-2% Ni bound in goethite which is highly enriched due to very strong leaching of magnesium and silicium. Beneath this zone nickel silicate ore can be formed, frequently containing > 2% Ni that is incorporated in silicates above all serpentine minerals. 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. Absence of this zone is due to erosion. Serpentinite is a rock comprised of an admixture of serpentine minerals. ... Dunite is an igneous, plutonic rock, of ultramafic composition, with coarse grained or phaneritic texture. ... Peridotite Peridotite is a dense, coarse-grained rock, consisting mostly of the minerals olivine and pyroxene. ... Limonite Limonite Limonite is a ferric hydrate of varying composition, the generic formula is frequently written as FeO(OH)·nH2O, although this is not entirely accurate as Limonite often contains a varying amount of oxide compared to hydroxide. ... In chemistry, a silicate is a compound consisting of silicon and oxygen (SixOy), one or more metals, and possibly hydrogen. ... Serpentine Serpentine is a group of common rock-forming hydrous magnesium iron phyllosilicate ((Mg, Fe)3Si2O5(OH)4) minerals; it is also often rich in other metal ores, including chromium, manganese, cobalt and nickel. ... Garnierite Garnierite is a mineral composed of hydrous nickel silicates a member of the serpentine group with formula: (Ni,Mg)3Si2O5(OH). ...

See also Oxisol, the more recent name for some laterite soils. Oxisols are an order in USA soil taxonomy, best known for their occurrence in tropical rain forest, 15-25 degrees north and south of the Equator. ...

References

Aleva,G.J.J.(Compiler) (1994): Laterites. Concepts, Geology, Morphology and Chemistry.169 pp. ISRIC, Wageningen, The Netherlands, ISBN 90-6672-053-0

Bardossy, G. and Aleva, G.J.J.(1990): Lateritic Bauxites. 624 pp. Developments in Economic Geology 27, ELSEVIER, ISBN 0-444-98811-4

Golightly, J.P. (1981): Nickeliferous Laterite Deposits. Economic Geology 75, 710-735

Schellmann, W. (1983): Geochemical principles of lateritic nickel ore formation. Proceedings of the 2. International Seminar on Lateritisation Processes, Sao Paulo, 119-135