Laterite

2026-08-21T12:27:17Z

2402:8100:2EED:F050:B8B1:7CFF:FE44:FC38: I've added a source for laterite

{{short description|Product of rock weathering in wet tropical climate rich in iron and aluminium}}
[[File:Laterite stone temple.jpg|thumb|Traditional laterite temple in Kerala]]
[[File:Laterite monument. C 002.jpg|thumb|alt=This monument is constructed of laterite brickstones. It commemorates Buchanan who first described laterite at this site.|Monument of laterite brickstones at [[Angadipuram]], [[Kerala]], India, which commemorates where laterite was first described and discussed by [[Francis Buchanan-Hamilton|Buchanan-Hamilton]] in 1807]]

'''Laterite''' is both a soil and a rock type rich in [[iron]] and [[aluminium]] and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high [[iron oxide]] content. They develop by intensive and prolonged [[weathering]] of the underlying [[parent rock]], usually when there are conditions of high temperatures and heavy rainfall with alternate wet and dry periods.<ref name=":0">{{cite book|last=Veena|first=Bhargava|title=Textbook of Geography - Grade 10}}</ref> Tropical weathering ('''''laterization'''''{{fact|date=October 2022}}) is a prolonged process of chemical weathering which produces a wide variety in the thickness, grade, chemistry and ore [[mineralogy]] of the resulting soils. The majority of the land area containing laterites is between the tropics of [[Tropic of Cancer|Cancer]] and [[Tropic of Capricorn|Capricorn]].

Laterite has commonly been referred to as a soil type as well as being a rock type. This, and further variation in the modes of conceptualizing about laterite (e.g. also as a complete weathering profile or theory about weathering), has led to calls for the term to be abandoned altogether. At least a few researchers {{who|date=May 2019}} specializing in [[regolith]] development have considered that hopeless confusion has evolved around the name. Material that looks highly similar to the Indian laterite occurs abundantly worldwide.

Historically, laterite was cut into brick-like shapes and used in monument-building. After 1000 CE, construction at [[Angkor Wat]] and other southeast Asian sites changed to rectangular temple enclosures made of laterite, brick, and stone. Since the mid-1970s, some trial sections of [[bituminous]]-surfaced, low-volume roads have used laterite in place of stone as a base course. Thick laterite layers are porous and slightly permeable, so the layers can function as [[aquifer]]s in rural areas. Locally available laterites have been used in an acid solution, followed by precipitation to remove [[Sewage treatment#Phosphorus removal|phosphorus]] and heavy metals at sewage-treatment facilities.

[https://lateritestone.com Laterites] are a source of aluminum [[ore]]; the ore exists largely in [[clay mineral]]s and the [[hydroxide]]s, [[gibbsite]], [[boehmite]], and [[diaspore]], which resembles the composition of [[bauxite]]. In [[Northern Ireland]] they once provided a major source of iron and aluminum ores. Laterite ores also were the early major source of [[nickel]].

==Definition and physical description==
[[File:Da ong Laterite.JPG|thumb|Laterite in [[Sơn Tây]], [[Hanoi]], [[Vietnam]]]]
[[Francis Buchanan-Hamilton]] first described and named a laterite formation in southern [[India]] in 1807.<ref name=archive/>{{rp|65}} He named it laterite from the [[Latin]] word ''[[:wikt:later#Latin|later]]'', which means a brick; this highly compacted and [[Cementation (geology)|cemented]] soil can easily be cut into brick-shaped blocks for building.<ref name=archive>{{cite book|title=The Madras Presidency, With Mysore, Coorg and the Associated States, Provincial Geographies of India|author=Thurston, Edgar|author-link = Edgar Thurston|date=1913|publisher=Cambridge University Press|url=https://archive.org/stream/provincialgeogra03holluoft#page/65/mode/1up|access-date=April 6, 2010}}</ref>{{rp|65}} The word ''laterite'' has been used for variably cemented, [[sesquioxide]]-rich [[soil horizon]]s.<ref name=helgren>{{cite journal|title=Paleosols of the Southern Cape Coast, South Africa: Implications for Laterite Definition, Genesis, and Age|author1=Helgren, David M.|author2=Butzer, Karl W. Butzer|journal=Geographical Review|volume=67|pages=430–445|number=4|date=October 1977|jstor=213626|doi=10.2307/213626}}</ref> A sesquioxide is an [[oxide]] with three atoms of oxygen and two metal atoms. It has also been used for any reddish soil at or near the Earth's surface.<ref name=helgren/>

Laterite covers are thick in the stable areas of the [[Western Ethiopian Shield]], on [[craton]]s of the South American Plate, and on the [[Australian Shield]].<ref name=tardy/>{{rp|1}} In [[Madhya Pradesh]], India, the laterite which caps the plateau is {{convert|30|m|ft|-1|abbr=on}} thick.<ref name=recent>{{cite report|title=Recent Concepts on the Origin of Indian Laterite|author1=Chowdhury, M.K. Roy|author2=Venkatesh, V.|author3=Anandalwar, M.A.|author4=Paul, D.K.|publisher=Geological Survey of India, Calcutta|date=May 11, 1965|url=http://www.new.dli.ernet.in/rawdataupload/upload/insa/INSA_1/20005ab9_547.pdf|access-date=April 17, 2010|url-status=dead|archive-url=https://web.archive.org/web/20120316083403/http://www.new.dli.ernet.in/rawdataupload/upload/insa/INSA_1/20005ab9_547.pdf|archive-date=March 16, 2012}}</ref>{{rp|554}} Laterites can be either soft and easily broken into smaller pieces, or firm and physically resistant. [[Basement (geology)|Basement]] rocks are buried under the thick weathered layer and rarely exposed.<ref name=tardy/>{{rp|1}} Lateritic soils form the uppermost part of the laterite cover.

In some places laterites contain [[pisolite]]s and [[ferricrete]], and they may be found in elevated positions as result of [[relief inversion]].<ref name=ZeitSouthSudan>{{cite journal|title=Morphogenese der südsudanischen Pediplane|journal=[[Zeitschrift für Geomorphologie]]|last=Fölster|first=Horst|volume=8|pages=393–423|issue=4|year=1964|language=German}}</ref>

[[Cliff Ollier]] has criticized the usefulness of the concept given that it is used to mean different things to different authors.<ref name=ollier1988/> Reportedly some have used it for ferricrete, others for tropical red earth soil, and yet others for soil profiles made, from top to bottom, of a [[duricrust|crust]], a mottled zone and a pallid zone.<ref name=ollier1988/> He cautions strongly against the concept of "lateritic deep weathering" since "it begs so many questions".<ref name=ollier1988>{{cite journal |title=Deep weathering, groundwater and climate |journal=[[Geografiska Annaler]] |last=Ollier |first=Cliff D. |issue=4 |volume=70 A |pages=285–290 |year=1988 |doi=10.1080/04353676.1988.11880258 |author-link=Cliff Ollier}}</ref>

==Formation==
[[File:Laterite-saprolite cross section.PNG|thumb|upright=1.25|alt=This diagram shows the position of laterite under residual soils and the ferruginous zone.|Laterite is often located under residual soils.]]
[[File:Estructura-suelo.jpg|thumb|upright=1.25|Soil layers, from soil down to bedrock: A represents [[soil]]; B represents laterite, a [[regolith]]; C represents [[saprolite]], a less-weathered regolith; below C is [[bedrock]]]]

Tropical weathering (laterization) is a prolonged process of chemical weathering which produces a wide variety in the thickness, grade, chemistry and ore mineralogy of the resulting soils.<ref name=dalvi/>{{rp|3}} The initial products of weathering are essentially kaolinized rocks called [[saprolite]]s.<ref name=schellmann >{{Cite web |title=An Introduction in Laterite |last=Schellmann |first=W |url=http://www.laterite.de |access-date=2022-01-25 |archive-date=2021-12-23 |archive-url=https://web.archive.org/web/20211223200908/http://www.laterite.de/ |url-status=live }}</ref> A period of active laterization extended from about the mid-[[Tertiary]] to the mid-[[Quaternary]] periods (35 to 1.5 million years ago).<ref name=dalvi/>{{rp|3}} Statistical analyses show that the transition in the mean and variance levels of 18O during the middle of the Pleistocene was abrupt.<ref name=maasch>{{cite journal|title=Statistical Detection of the mid-Pleistocene Transition|journal=Climate Dynamics|issn=0930-7575|volume=2|issue=3|date=February 1988|doi=10.1007/BF01053471|pages=133–143|author=Maasch, K.A.|bibcode=1988ClDy....2..133M|s2cid=129849310}}</ref> It seems this abrupt change was global and mainly represents an increase in ice mass; at about the same time an abrupt decrease in [[sea surface temperature]]s occurred; these two changes indicate a sudden global cooling.<ref name=maasch/> The rate of laterization would have decreased with the abrupt cooling of the earth. Weathering in tropical climates continues to this day, at a reduced rate.<ref name=dalvi/>{{rp|3}}

Laterites are formed from the [[Leaching (pedology)|leaching]] of parent [[sedimentary rock]]s ([[sandstone]]s, [[clay]]s, [[limestone]]s); [[metamorphic rock]]s ([[schist]]s, [[gneiss]]es, [[migmatite]]s); [[igneous rock]]s ([[granite]]s, [[basalt]]s, [[gabbro]]s, [[peridotite]]s); and mineralized proto-ores;<ref name=tardy/>{{rp|5}} which leaves the more [[Solubility#Solubility of ionic compounds in water|insoluble]] ions, predominantly iron and aluminum. The mechanism of leaching involves acid dissolving the host [[mineral]] [[Crystal structure#Lattice systems|lattice]], followed by hydrolysis and precipitation of insoluble oxides and sulfates of iron, aluminum and silica under the high temperature conditions<ref name=muir/> of a humid sub-tropical [[monsoon]] [[climate]].<ref name=hill/>

An essential feature for the formation of laterite is the repetition of [[Wet season|wet]] and [[dry season]]s.<ref name=kosei>{{cite report|title=Iron isotope compositions of Fe-oxide as a measure of water-rock interaction: An example from Precambrian tropical laterite in Botswana|author=Yamaguchi, Kosei E.|series=Frontier Research on Earth Evolution|volume=2|date=2003{{ndash}}2004|page=3|url=http://www.jamstec.go.jp/ifree/jp/05result/IFREE_Report_for_2003-2004/honbun/04_26.pdf|access-date=April 17, 2010}}{{Dead link|date=February 2020 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Rocks are leached by percolating rain water during the wet season; the resulting solution containing the leached ions is brought to the surface by [[capillary action]] during the dry season.<ref name=kosei/> These ions form soluble [[Salt (chemistry)|salt compounds]] which dry on the surface; these salts are washed away during the next wet season.<ref name=kosei/> Laterite formation is favored in low [[Terrain|topographical relief]]s of gentle crests and [[plateau]]s which prevents erosion of the surface cover.<ref name=dalvi/>{{rp|4}} The reaction zone where rocks are in contact with water—from the lowest to highest [[water table]] levels—is progressively depleted of the easily leached ions of [[sodium]], [[potassium]], [[calcium]] and [[magnesium]].<ref name=kosei/> A solution of these [[ion]]s can have the correct [[pH]] to preferentially dissolve [[silicon oxide]] rather than the [[aluminum oxide]]s and [[iron oxide]]s.<ref name=kosei/> [[Silcrete]] has been suggested to form in zones inrelatively dry "precipitating zones" of laterites.<ref name=oll84-116>{{Cite book |title=Weathering |last=Ollier |first=Cliff |year=1984 |edition=2nd |pages=116 |chapter=Hydrology and weathering |author-link=Cliff Ollier |orig-date=1969}}</ref> To the contrary, in the wetter parts of laterites subject to leaching [[ferricrete]]s have been suggested to form.<ref name=oll84-116/>

The mineralogical and chemical compositions of laterites are dependent on their parent rocks.<ref name=tardy/>{{rp|6}} Laterites consist mainly of [[quartz]], [[zircon]], and oxides of [[titanium]], iron, [[tin]], aluminum and [[manganese]], which remain during the course of weathering.<ref name=tardy/>{{rp|7}} Quartz is the most abundant relic mineral from the parent rock.<ref name=tardy/>{{rp|7}}

Laterites vary significantly according to their location, climate and depth.<ref name=muir/> The main host minerals for nickel and [[cobalt]] can be either [[iron oxide]]s, [[clay mineral]]s or [[manganese oxide]]s.<ref name=muir>{{cite journal|title=Pressure Acid Leaching of Nickel Laterites: A Review|author1=Whittington, B.I.|author2=Muir, D.|journal=Mineral Processing and Extractive Metallurgy Review|volume=21|issue=6|date=October 2000|pages=527–599|doi=10.1080/08827500008914177|bibcode=2000MPEMR..21..527W |s2cid=96783165}}</ref> Iron oxides are derived from [[mafic]] [[igneous rock]]s and other iron-rich rocks; [[bauxite]]s are derived from [[granitic]] igneous rock and other iron-poor rocks.<ref name=kosei/> Nickel laterites occur in zones of the earth which experienced prolonged tropical weathering of [[ultramafic rock]]s containing the ferro-magnesian minerals [[olivine]], [[pyroxene]], and [[amphibole]].<ref name=dalvi/>{{rp|3}}

==Locations==
Yves Tardy, from the ''French [[National Polytechnic Institute of Toulouse|Institut National Polytechnique de Toulouse]]'' and the ''Centre National de la Recherche Scientifique'', calculated that laterites cover about one-third of the Earth's continental land area.<ref name=tardy/>{{rp|1}} Lateritic soils are the [[subsoil]]s of the equatorial forests, of the [[savanna]]s of the humid tropical regions, and of the [[Sahel]]ian [[steppes]].<ref name=tardy/>{{rp|1}} They cover most of the land area between the tropics of Cancer and Capricorn; areas not covered within these latitudes include the extreme western portion of South America, the southwestern portion of Africa, the desert regions of north-central Africa, the Arabian peninsula and the interior of Australia.<ref name=tardy/>{{rp|2}}

Some of the oldest and most highly deformed ultramafic rocks which underwent laterization are found as petrified fossil soils in the complex [[Precambrian]] shields in Brazil and Australia.<ref name=dalvi/>{{rp|3}} Smaller highly deformed [[Alpine orogeny|Alpine-type]] intrusives have formed laterite profiles in Guatemala, Colombia, Central Europe, India and Burma.<ref name=dalvi/>{{rp|3}} Large thrust sheets of [[Mesozoic]] [[island arc]]s and [[continental collision]] zones underwent laterization in New Caledonia, Cuba, Indonesian and the Philippines.<ref name=dalvi/>{{rp|3}} Laterites reflect past weathering conditions;<ref name=helgren/> laterites which are found in present-day non-tropical areas are products of former [[Supercontinents|geological epochs]], when that area was near the equator. Present-day laterite occurring outside the humid tropics are considered to be indicators of climatic change, continental drift or a combination of both.<ref>{{cite journal|title=Perennial problems in the study of laterite: A review|author=Bourman, R.P.|journal=Australian Journal of Earth Sciences|volume=40|issue=4|date=August 1993|pages=387–401|doi=10.1080/08120099308728090|bibcode=1993AuJES..40..387B}}</ref> In India, laterite soils occupy an area of 240,000 square kilometres <ref name=":0" />

==Uses==

===Agriculture===
Laterite soils have a high clay content, which means they have higher [[cation exchange capacity]], low permeability, high plasticity and high water-holding capacity than sandy soils. It is because the particles are so small, the water is trapped between them. After the rain, the water moves into the soil slowly. Due to intensive leaching, laterite soils lack in fertility in comparison to other soils, however they respond readily to manuring and irrigation.<ref name=":0" /> Palms are less likely to suffer from drought because the rainwater is held in the soil. However, if the structure of lateritic soils becomes degraded, a hard crust can form on the surface, which hinders water infiltration, the emergence of seedlings, and leads to increased runoff. It is possible to rehabilitate such soils, using a system called the 'bio-reclamation of degraded lands'. This involves using indigenous water-harvesting methods (such as planting pits and trenches), applying animal and plant residues, and planting high-value fruit trees and indigenous vegetable crops that are tolerant of drought conditions. These soils are most suitable for plantation crops. They are good for oil palm, tea, coffee and cashew cultivation. The [[International Crops Research Institute for the Semi-Arid Tropics]] ([[ICRISAT]]) has employed this system to rehabilitate degraded laterite soils in [[Niger]] and increase [[smallholding|smallholder]] farmers' incomes.<ref>[http://www.icrisat.org/impacts/impact-stories/Converting-degraded-soils-into-productive-land.pdf ''Bio-reclamation – Converting degraded lateritic soils into productive land''] {{Webarchive|url=https://web.archive.org/web/20180726233807/http://www.icrisat.org/impacts/impact-stories/Converting-degraded-soils-into-productive-land.pdf |date=2018-07-26 }}, Rural 21, March 2013.</ref> In some places, these soils support grazing grounds and scrub forests. <ref name=":0" />

===Building blocks===
[[File:Laterite quarry, Angadipuram, India. C 004.jpg|thumb|upright|alt=A man is cutting laterite into brickstones in Angadipuram, India.|Cutting laterite bricks in Angadipuram, India]]
[[File:Pre Rup, Angkor, Camboya, 2013-08-16, DD 04.JPG|thumb|upright|Example of construction with laterite in [[Pre Rup]], [[Angkor]], [[Cambodia]].]]
When moist, laterites can easily be cut with a spade into regular-sized blocks.<ref name=tardy>{{cite book|title=Petrology of Laterites and Tropical Soils|author=Tardy, Yves|isbn=978-90-5410-678-4|date=1997|url=https://books.google.com/books?id=n9cdaPZr1RwC&q=laterite+definition&pg=PA1|access-date=April 17, 2010|archive-date=October 23, 2021|archive-url=https://web.archive.org/web/20211023135039/https://books.google.com/books?id=n9cdaPZr1RwC&q=laterite+definition&pg=PA1|url-status=live}}</ref>{{rp|1}} Laterite is mined while it is below the water table, so it is wet and soft.<ref name=engelhardt>{{cite report|title=New Directions for Archaeological Research on the Angkor Plain: The Use of Remote Sensing Technology for Research into Ancient Khmer Environmental Engineering|author=Engelhardt, Richard A.|publisher=UNESCO|page=8|url=http://ejournal.anu.edu.au/index.php/bippa/article/viewFile/440/429|access-date=April 17, 2010|archive-url=https://web.archive.org/web/20090922103448/http://ejournal.anu.edu.au/index.php/bippa/article/viewFile/440/429|archive-date=2009-09-22|url-status=dead}}</ref> Upon exposure to air it gradually hardens as the moisture between the flat clay particles evaporates and the larger iron salts<ref name=kosei/> lock into a rigid [[Crystal structure#Lattice systems|lattice structure]]<ref name=engelhardt/>{{rp|158}} and become resistant to atmospheric conditions.<ref name=tardy/>{{rp|1}} The art of quarrying laterite material into [[masonry]] is suspected to have been introduced from the Indian subcontinent.{{clarify|date=August 2015}}<ref>{{cite journal|title=Ancient Khmer Quarrying of Arkose Sandstone for Monumental Architecture and Sculpture|author=Rocks, David|publisher=Proceedings of the Third International Congress on Construction History|date=May 2009|page=1235|url=http://www-docs.tu-cottbus.de/bautechnikgeschichte/public/openaccess/rocks_oa.pdf|access-date=April 17, 2010}}{{Dead link|date=November 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> They harden like iron when they are exposed to air. <ref name=":0" />

After 1000 CE Angkorian construction changed from circular or irregular earthen walls to rectangular temple enclosures of laterite, brick and stone structures.<ref name=welch>{{cite journal|title=Archaelological Evidence of Khmer State Political and Economic Organisation|author=Welch, David|publisher=International Archaeological Research Institute|url=http://ejournal.anu.edu.au/index.php/bippa/article/viewFile/377/366|access-date=April 17, 2010|archive-url=https://web.archive.org/web/20090919221431/http://ejournal.anu.edu.au/index.php/bippa/article/viewFile/377/366|archive-date=2009-09-19|url-status=dead}}</ref>{{rp|3}} Geographic surveys show areas which have laterite stone alignments which may be foundations of temple sites that have not survived.<ref name=welch/>{{rp|4}} The Khmer people constructed the Angkor monuments—which are widely distributed in Cambodia and Thailand—between the 9th and 13th centuries.<ref name=uchida>{{cite journal|title=The Construction Process of the Angkor Monuments Elucidated by the Magnetic Susceptibility of Sandstone|author1=Uchinda, E.|author2=Cunin, O.|author3=Shimoda, I.|author4=Suda, C.|author5=Nakagawa, T.|journal=Archaeometry|volume=45|issue=2|date=2003|url=http://www.crai.archi.fr/media/pdf/ARCH4502.pdf|access-date=May 6, 2010|doi=10.1111/1475-4754.00105|pages=221–232|archive-url=https://web.archive.org/web/20110720204127/http://www.crai.archi.fr/media/pdf/ARCH4502.pdf|archive-date=2011-07-20|url-status=dead|citeseerx=10.1.1.492.4177}}</ref>{{rp|209}} The stone materials used were sandstone and laterite; brick had been used in monuments constructed in the 9th and 10th centuries.<ref name=uchida/>{{rp|210}} Two types of laterite can be identified; both types consist of the minerals kaolinite, quartz, hematite and goethite.<ref name=uchida/>{{rp|211}} Differences in the amounts of minor elements arsenic, antimony, vanadium and strontium were measured between the two laterites.<ref name=uchida/>{{rp|211}}

[[Angkor Wat]]—located in present-day Cambodia—is the largest religious structure built by [[Suryavarman II]], who ruled the [[Khmer Empire]] from 1112 to 1152.<ref name=waragai>{{cite report|title=A Preliminary Study on the Direction Dependence of Sandstone Column Deterioration in the First Gallery of Angkor Wat|author1=Waragai, Tetsuya|author2=Katagiri, Masao|author3=Miwa, Satoru|series=Proceedings of the Institute of Natural Sciences, Nihon University|date=2006|number=41|url=http://www.chs.nihon-u.ac.jp/institute/nature/kiyou/2006/pdf/1_4.pdf|access-date=May 6, 2010|archive-date=October 3, 2011|archive-url=https://web.archive.org/web/20111003185244/http://www.chs.nihon-u.ac.jp/institute/nature/kiyou/2006/pdf/1_4.pdf|url-status=live}}</ref>{{rp|39}} It is a World Heritage site.<ref name=waragai/>{{rp|39}} The sandstone used for the building of Angkor Wat is Mesozoic sandstone quarried in the Phnom Kulen Mountains, about {{convert|40|km|mi|abbr=on}} away from the temple.<ref name=jw>{{cite report|title=Salt Load and Deterioration of Sandstone at the Temple of Angkor Wat, Cambodia|author1=Siedel, H.|author2=Plehwe-Leisen, E. v.|author3=Leisen, H.|series=11th International Congress on Deterioration and Conservation of Stone, Torun, Poland|date=2008|volume=I|page=268|url=http://elearn.hawk-hhg.de/projekte/salzwiki/media/E-Publication/Angkor_2008_Torun.pdf|access-date=May 6, 2010|archive-date=July 19, 2011|archive-url=https://web.archive.org/web/20110719035116/http://elearn.hawk-hhg.de/projekte/salzwiki/media/E-Publication/Angkor_2008_Torun.pdf|url-status=live}}</ref> The foundations and internal parts of the temple contain laterite blocks behind the sandstone surface.<ref name=jw/> The masonry was laid without joint mortar.<ref name=jw/>

===Road building===
[[File:Laterite-Casamance.jpg|thumb|left|alt=This shows a laterite road near Kounkane, Upper Casamance, Senegal. It resembles a red graveled road.|Laterite road near Kounkane, Upper Casamance, Senegal]]

[[French colonial empire|The French]] surfaced roads in the Cambodia, Thailand and Vietnam area with crushed laterite, stone or gravel.<ref>{{cite journal|title=The Trade Route in the Cambodian/Thai Border Areas: Challenges and Opportunities|author=Sari, Betti Rosita|page=6|journal=Journal of Masyarakat Indonesia|date=2004|url=http://katalog.pdii.lipi.go.id|access-date=April 17, 2010|archive-date=April 14, 2010|archive-url=https://web.archive.org/web/20100414070006/http://katalog.pdii.lipi.go.id/|url-status=live}}</ref> Kenya, during the mid-1970s, and Malawi, during the mid-1980s, constructed trial sections of bituminous-surfaced low-volume roads using laterite in place of stone as a base course.<ref name=grace>{{cite journal|title=Investigations in Kenya and Malawi using as-dug laterite as bases for bituminous surfaced roads|author=Grace, Henry|journal=Journal Geotechnical and Geological Engineering|volume=9|issue=3–4|date=September 1991|doi=10.1007/BF00881740|pages=183–195|s2cid=128492633}}</ref> The laterite did not conform with any accepted specifications but performed equally well when compared with adjoining sections of road using stone or other stabilized material as a base.<ref name=grace/> In 1984 US$40,000 per {{convert|1|km|mi|abbr=on}} was saved in Malawi by using laterite in this way.<ref name=grace/>

===Water supply===
Bedrock in tropical zones is often granite, gneiss, schist or sandstone; the thick laterite layer is porous and slightly permeable so the layer can function as an aquifer in rural areas.<ref name=tardy/>{{rp|2}} One example is the Southwestern Laterite (Cabook) Aquifer in Sri Lanka.<ref name=cr/>{{rp|1}} This aquifer is on the southwest border of Sri Lanka, with the narrow Shallow Aquifers on Coastal Sands between it and the ocean.<ref name=cr/>{{rp|4}} It has the considerable water-holding capacity, depending on the depth of the formation.<ref name=cr>{{cite report|title=Groundwater Resources of Sri Lanka|author1=Panabokke, C.R.|author2=Perera, A.P.G.R.L.|publisher=Water Resources Board|date=January 2005|url=http://tsunami.obeysekera.net/documents/Panabokke_Perera_2005_Sri_Lanka.pdf|access-date=April 17, 2010|archive-date=January 3, 2011|archive-url=https://web.archive.org/web/20110103060325/http://tsunami.obeysekera.net/documents/Panabokke_Perera_2005_Sri_Lanka.pdf|url-status=live}}</ref>{{rp|1}} The aquifer in this laterite recharges rapidly with the rains of April–May which follow the dry season of February–March, and continues to fill with the [[monsoon]] rains.<ref name=cr/>{{rp|10}} The water table recedes slowly and is recharged several times during the rest of the year.<ref name=cr/>{{rp|13}} In some high-density suburban areas the water table could recede to {{convert|15|m|ft|-1|abbr=on}} below ground level during a prolonged dry period of more than 65 days.<ref name=cr/>{{rp|13}} The Cabook Aquifer laterites support relatively shallow aquifers that are accessible to dug wells.<ref name=cr/>{{rp|10}}

===Waste water treatment===
In Northern Ireland, phosphorus enrichment of lakes due to agriculture is a significant problem.<ref name=wood>{{cite journal|title=Constructed wetlands for waste water treatment: the use of laterite in the bed medium in phosphorus and heavy metal removal|author1=Wood, R. B.|author2=McAtamney, C.F.|journal=Hydrobiologia|volume=340|number=1–3|date=December 1996|doi=10.1007/BF00012776|pages=323–331|s2cid=6182870}}</ref> Locally available laterite—a low-grade bauxite rich in iron and aluminum—is used in acid solution, followed by precipitation to remove phosphorus and heavy metals at several sewage treatment facilities.<ref name=wood/> Calcium-, iron- and aluminum-rich solid media are recommended for phosphorus removal.<ref name=wood/> A study, using both laboratory tests and pilot-scale constructed wetlands, reports the effectiveness of granular laterite in removing phosphorus and heavy metals from landfill [[leachate]].<ref name=wood/> Initial laboratory studies show that laterite is capable of 99% removal of phosphorus from solution.<ref name=wood/> A pilot-scale experimental facility containing laterite achieved 96% removal of phosphorus.<ref name=wood/> This removal is greater than reported in other systems.<ref name=wood/> Initial removals of aluminum and iron by pilot-scale facilities have been up to 85% and 98% respectively.<ref name=wood/> Percolating columns of laterite removed enough [[cadmium]], [[chromium]] and [[lead]] to undetectable concentrations.<ref name=wood/> There is a possible application of this low-cost, low-technology, visually unobtrusive, efficient system for rural areas with dispersed point sources of pollution.<ref name=wood/>

===Ores===
[[File:K Laterite.JPG|thumb|right|[[Cretaceous]] iron-rich laterite (the dark unit) in [[Hamakhtesh Hagadol]], southern [[Israel]].]]

Ores are concentrated in metalliferous laterites; aluminum is found in [[bauxite]]s, iron and manganese are found in iron-rich hard crusts, nickel and copper are found in disintegrated rocks, and gold is found in mottled clays.<ref name=tardy/>{{rp|2}}

====Bauxite====
[[File:Bauxite section on kaolinitic sandstone C 007.jpg|thumb|left|alt=Bauxite on white kaolinitic sandstone at Pera Head, Weipa, Australia.|Bauxite on white kaolinitic sandstone at Pera Head, Weipa, Australia]]
[[File:Absolute iron accumulation in kaolinized basalt. C 015.jpg|thumb|alt=This rock wall shows dark veins of mobilized and precipitated iron within kaolinized basalt in Hungen, Vogelsberg area, Germany. The dark veins are precipitated iron within kaolinized basalt near Hungen, Vogelsberg, Germany.]]

[[Bauxite]] ore is the main source of aluminum.<ref name=archive/>{{rp|65}} Bauxite is a variety of laterite (residual sedimentary rock), so it has no precise chemical formula.<ref name=fc/> It is composed mainly of hydrated alumina minerals such as [[gibbsite]] [Al(OH)3 or Al2O3 . 3H2O)] in newer tropical deposits; in older subtropical, temperate deposits the major minerals are [[boehmite]] [γ-AlO(OH) or Al2O3.H2O] and some [[diaspore]] [α-AlO(OH) or Al2O3.H2O].<ref name=fc/> The average chemical composition of bauxite, by weight, is 45 to 60% Al2O3 and 20 to 30% Fe2O3.<ref name=fc/> The remaining weight consists of silicas (quartz, [[chalcedony]] and [[kaolinite]]), carbonates ([[calcite]], [[magnesite]] and [[Dolomite (mineral)|dolomite]]), titanium dioxide and water.<ref name=fc>{{cite book|title=Material Handbook: A Concise Desktop Reference|url=https://archive.org/details/materialshandbo00card|url-access=limited|author=Cardarelli, Francois|page=[https://archive.org/details/materialshandboo00card/page/n632 601]|publisher=Springer|date=2008|isbn=9781846286681}}</ref> Bauxites of economical interest must be low in kaolinite.<ref name=schellmann /> Formation of lateritic bauxites occurs worldwide in the 145- to 2-million-year-old [[Cretaceous]] and Tertiary coastal plains.<ref name=ida>{{cite journal|title=Palaeoenvironment of lateritic bauxites with vertical and lateral differentiation|author=Valeton, Ida|journal=Geological Society, London, Special Publications|date=1983|volume=11|issue=1|pages=77–90|url=http://sp.lyellcollection.org/cgi/content/abstract/11/1/77|access-date=April 17, 2010|doi=10.1144/gsl.sp.1983.011.01.10|bibcode=1983GSLSP..11...77V|s2cid=128495695|author-link=Ida Valeton|archive-date=January 12, 2011|archive-url=https://web.archive.org/web/20110112223017/http://sp.lyellcollection.org/cgi/content/abstract/11/1/77|url-status=live}}</ref> The bauxites form elongate belts, sometimes hundreds of kilometers long, parallel to Lower Tertiary shorelines in India and South America; their distribution is not related to a particular mineralogical composition of the parent rock.<ref name=ida/> Many high-level bauxites are formed in coastal plains which were subsequently uplifted to their present altitude.<ref name=ida/>

====Iron====
[[File:Laterite formation on serpentinite. C 008.jpg|thumb|upright|alt=This photograph shows the irregular weathering of the grey serpentinite to the greyish-brown nickel-containing laterite with a high iron percentage (nickel limonite). This was taken near Mayaguex, Puerto Rico.|Irregular weathering of grey [[serpentinite]] to greyish-brown nickel-containing laterite with a high iron percentage (nickel [[limonite]]), near Mayagüez, Puerto Rico.]]

The basaltic laterites of [[Northern Ireland]] were formed by extensive chemical weathering of [[basalt]]s during a period of volcanic activity.<ref name=hill>{{cite journal|title=Geochemical evolution of a palaeolaterite: the Interbasaltic Formation, Northern Ireland|author1=Hill, I. G.|author2=Worden, R. H.|author3=Meighan, I. G.|journal=Chemical Geology|volume=166|issue=1–2|date=May 1, 2000|pages=65–84|doi=10.1016/S0009-2541(99)00179-5|bibcode=2000ChGeo.166...65H}}</ref> They reach a maximum thickness of {{convert|30|m|ft|-1|abbr=on}} and once provided a major source of iron and aluminum ore.<ref name=hill/> Percolating waters caused degradation of the parent basalt and preferential precipitation by acidic water through the lattice left the iron and aluminum ores.<ref name=hill/> Primary [[olivine]], [[plagioclase]] [[feldspar]] and [[augite]] were successively broken down and replaced by a mineral assemblage consisting of [[hematite]], [[gibbsite]], [[goethite]], [[anatase]], [[halloysite]] and [[kaolinite]].<ref name=hill/>

====Nickel====
{{main|Lateritic nickel ore deposits}}

Laterite ores were the major source of early nickel.<ref name=dalvi>{{cite report|title=The Past and the Future of Nickel Laterites|author1=Dalvi, Ashok D.|author2=Bacon, W. Gordon|author3=Osborne, Robert C.|publisher=PDAC 2004 International Convention, Trade Show & Investors Exchange|date=March 7–10, 2004|url=http://www.pdac.ca/pdac/publications/papers/2004/techprgm-dalvi-bacon.pdf|access-date=April 17, 2010|archive-url=https://web.archive.org/web/20091104193348/http://www.pdac.ca/pdac/publications/papers/2004/techprgm-dalvi-bacon.pdf|archive-date=2009-11-04|url-status=dead}}</ref>{{rp|1}} Rich laterite deposits in [[Nickel mining in New Caledonia|New Caledonia]] were mined starting the end of the 19th century to produce [[white metal]].<ref name=dalvi/>{{rp|1}} The discovery of sulfide deposits of [[Sudbury Basin|Sudbury]], Ontario, Canada, during the early part of the 20th century shifted the focus to [[Sulfide mineral|sulfides]] for nickel extraction.<ref name=dalvi/>{{rp|1}} About 70% of the Earth's land-based [[nickel]] resources are contained in laterites; they currently account for about 40% of the world nickel production.<ref name=dalvi/>{{rp|1}} In 1950 laterite-source nickel was less than 10% of total production, in 2003 it accounted for 42%, and by 2012 the share of laterite-source nickel was expected to be 51%.<ref name=dalvi/>{{rp|1}} The four main areas in the world with the largest nickel laterite resources are New Caledonia, with 21%; Australia, with 20%; the Philippines, with 17%; and Indonesia, with 12%.<ref name=dalvi/>{{rp|4}}

==See also==
*[[Ferricrete]] – stony particles conglomerated into rock by oxidized iron compounds from ground water
*{{annotated link|Oxisol}}
*{{annotated link|Plinthosol}}
{{clear}}

==References==
{{reflist}}

{{Soil type}}
{{Rock type}}
{{Authority control}}

[[Category:Sedimentology]]
[[Category:Weathering]]
[[Category:Ore deposits]]
[[Category:Aluminium minerals]]
[[Category:Pedology]]
[[Category:Building materials]]
[[Category:Soil-based building materials]]
[[Category:Regolith]]

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Laterite