View source for Diatomaceous earth

{{Short description|Soft, siliceous sedimentary rock}}
{{Use American English|date=September 2021}}
{{Use mdy dates|date=February 2024}}
[[File:Diatomite (Sisquoc Formation, Miocene-Pliocene; Palos Colorados Quarry, California, USA) 5.jpg|thumb|upright=1.2|Diatomite rock sample from [[Sisquoc Formation]]]]
[[File:Ziemia okrzemkowa.JPG|thumb|upright=1.2|[[scanning electron microscope|Scanning electron]] [[micrograph]] of diatomaceous earth]]

'''Diatomaceous earth''' ({{IPAc-en|ˌ|d|aɪ|.|ə|t|ə|ˈ|m|eɪ|ʃ|ə|s}} {{respell|DY|ə|tə|MAY|shəs}}), also known as '''diatomite''' ({{IPAc-en|d|aɪ|ˈ|æ|t|ə|m|aɪ|t}} {{respell|dy|AT|ə|myte}}), '''celite''', or '''kieselguhr''', is a naturally occurring, soft, [[siliceous rock|siliceous]] [[sedimentary rock]] that can be crumbled into a fine white to off-white powder. It has a [[particle size]] ranging from more than 3&nbsp;[[millimeter|mm]] to less than 1&nbsp;[[micrometre|μm]], but typically 10 to 200&nbsp;μm.<ref>{{Cite journal |last1=Dobrosielska |first1=Marta |last2=Dobrucka |first2=Renata |last3=Brząkalski |first3=Dariusz |last4=Frydrych |first4=Miłosz |last5=Kozera |first5=Paulina |last6=Wieczorek |first6=Monika |last7=Jałbrzykowski |first7=Marek |last8=Kurzydłowski |first8=Krzysztof J. |last9=Przekop |first9=Robert E. |date=May 18, 2022 |title=Influence of Diatomaceous Earth Particle Size on Mechanical Properties of PLA/Diatomaceous Earth Composites |journal=Materials |language=en |volume=15 |issue=10 |pages=3607 |doi=10.3390/ma15103607 |doi-access=free |issn=1996-1944 |pmc=9145730 |pmid=35629631|bibcode=2022Mate...15.3607D }}</ref> Depending on the [[granularity]], this powder can have an [[abrasive]] feel, similar to [[pumice]] powder, and has a low [[density]] as a result of its high [[porosity]]. The typical chemical composition of oven-dried diatomaceous earth is 80–90% [[silica]], with 2–4% [[aluminum oxide|alumina]] (attributed mostly to [[clay mineral]]s), and 0.5–2% [[iron oxide]].<ref name="USGS">{{cite book |last=Antonides |first=Lloyd E. |title=Diatomite |year=1997 |publisher=[[United States Geological Survey|USGS]] |url=https://minerals.usgs.gov/minerals/pubs/commodity/diatomite/250497.pdf |access-date=December 12, 2010}}</ref>

Diatomaceous earth consists of the [[fossil]]ized remains of [[diatom]]s, a type of hard-shelled [[microalgae]], that have accumulated over millions of years.<ref name=":0">{{Cite journal |last1=Rojht |first1=Helena |last2=Horvat |first2=Aleksander |last3=Athanassiou |first3=Christos G. |last4=Vayias |first4=Bill J. |last5=Tomanović |first5=Željko |last6=Trdan |first6=Stanislav |date=2010–2012 |title=Impact of geochemical composition of diatomaceous earth on its insecticidal activity against adults of Sitophilus oryzae (L.) (Coleoptera: Curculionidae) |url=http://link.springer.com/10.1007/s10340-010-0313-6 |journal=Journal of Pest Science |language=en |volume=83 |issue=4 |pages=429–436 |doi=10.1007/s10340-010-0313-6 |bibcode=2010JPesS..83..429R |s2cid=23110767 |issn=1612-4758}}</ref> It is used as a [[filtration]] aid, mild abrasive in products including metal polishes and [[toothpaste]], mechanical [[insecticide]], [[absorption (chemistry)|absorbent]] for liquids, matting agent for coatings, reinforcing filler in plastics and rubber, anti-block in plastic films, porous support for chemical catalysts, [[Litter box|cat litter]], activator in [[coagulation]] studies, a stabilizing component of [[dynamite]], a [[thermal insulation|thermal insulator]], and a soil for potted plants and trees as in the art of [[bonsai]].<ref>{{cite journal |last1=Reka |first1=Arianit A. |last2=Pavlovski |first2=Blagoj |last3=Ademi |first3=Egzon |last4=Jashari |first4=Ahmed |last5=Boev |first5=Blazo |last6=Boev |first6=Ivan |last7=Makreski |first7=Petre |title=Effect Of Thermal Treatment Of Trepel At Temperature Range 800-1200˚C |journal=Open Chemistry |date=December 31, 2019 |volume=17 |issue=1 |pages=1235–1243 |doi=10.1515/chem-2019-0132|doi-access=free }}</ref><ref>{{cite journal |last1=Reka |first1=Arianit |last2=Anovski |first2=Todor |last3=Bogoevski |first3=Slobodan |last4=Pavlovski |first4=Blagoj |last5=Boškovski |first5=Boško |title=Physical-chemical and mineralogical-petrographic examinations of diatomite from deposit near village of Rožden, Republic of Macedonia |journal=Geologica Macedonica |date=December 29, 2014 |volume=28 |issue=2 |pages=121–126 |url=https://js.ugd.edu.mk/index.php/GEOLMAC/article/view/920}}</ref> It is also used in [[gas chromatography]] packed columns made with glass or metal as stationary phase.

== Composition ==
Diatomaceous earth consists of the fossilized remains of diatoms that accumulated over millions of years. It is usually composed of 80% to 90% silica, 2% to 4% alumina minerals, and 0.5% to 2% iron oxide, although the precise composition of every deposit is different.<ref name=":0" /> Deposits may contain different amounts of silica depending on the [[sedimentology|sedimentation conditions]], the presence of other sediments (clay, sand, volcanic ashes), and the age of the deposit ([[diagenesis]], [[silica]] (SiO<sub>2</sub>) dissolution/precipitation, diatoms tests ageing). The species of diatom may also differ among deposits. The species of diatom is dependent upon the age and [[paleoecology]] of the deposit. In turn, the shape of a diatom is determined by its species.

Many deposits throughout [[British Columbia]], such as Red Lake Earth, are from the [[Miocene]] epoch and contain a species of diatom known as ''Melosira granulata''. These diatoms have a small globular shape. A deposit containing diatoms from this epoch can provide certain benefits over others. For example, diatoms from the [[Eocene]] epoch are not as effective in their ability to absorb fluids because as older diatoms recrystallize, their small pores become filled with silica.<ref>{{cite web |title=Diatoms |url=https://www.ucl.ac.uk/GeolSci/micropal/diatom.html |publisher=UCL London's Global University |access-date=September 14, 2011}}</ref>

== Formation ==
{{biomineralization sidebar|silicification}}

Diatomite forms by the accumulation of the [[amorphous]] silica ([[opal]], {{chem2|SiO2*''n''H2O}}) remains of dead diatoms (microscopic single-celled [[algae]]) in [[lake sediment]] or [[marine sediment]]s. The [[fossil]] remains consist of a pair of symmetrical shells or [[frustule]]s.<ref name="USGS"/> Marine diatomites are found in association with a wide variety of other rock types but lacustrine diatomites are almost always associated with volcanic rock. Diatomaceous [[chert]] consists of diatomite that has been [[cementation (geology)|cemented]] with silica.<ref>{{cite book |last1=Boggs |first1=Sam |title=Principles of sedimentology and stratigraphy |date=2006 |publisher=Pearson Prentice Hall |isbn=0131547283 |edition=4th |location=Upper Saddle River, New Jersey |page=208}}</ref>

Diatoms are able to extract silica from water that is less than 1% saturated in amorphous silica (saturation index (SI): -2). Their frustules remain undissolved because they are surrounded by an organic matrix. Clay minerals may also precipitate on the frustules and protect them from dissolution in sea water. When the diatom dies, the frustule is stripped of its organic layer and exposed to sea water. As a result, only 1% to 10% of frustules survive long enough to be buried under sediments and some of this is dissolved within the sediments. Only an estimated 0.05% to 0.15% of the original amount of silica produced by diatoms is preserved in the sedimentary record.<ref>{{cite book |last1=Blatt |first1=Harvey |title=Origin of sedimentary rocks |last2=Middleton |first2=Gerard |last3=Murray |first3=Raymond |date=1980 |publisher=Prentice-Hall |isbn=0136427103 |edition=2d |location=Englewood Cliffs, New Jersey |pages=578–579}}</ref>

== Discovery ==
In 1836 or 1837, German peasant Peter Kasten discovered diatomaceous earth (German: ''Kieselgur''{{--)}} when sinking a well on the northern slopes of the [[Haußelberg]] hill, on [[Lüneburg Heath]] in [[North German Plain|North Germany]].<ref>{{cite book |last1=Ghobara |first1=Mohamed M |last2=Mazumder |first2=Nirmal |last3=Vinayak |first3=Vandana |last4=Reissig |first4=Louisa |last5=Gebeshuber |first5=Ille C |last6=Tiffany |first6=Mary Ann |last7=Gordon |first7=Richard |chapter=On Light and Diatoms: A Photonics and Photobiology Review |title=Diatoms: Fundamentals and Applications |series=Diatoms: Biology and Applications |date=June 28, 2019 |publisher=[[Wiley (publisher)|Wiley-Scrivener]] |location=Hoboken, New Jersey |page=475 |doi=10.1002/9781119370741.ch7 |isbn=978-1-119-37021-5 |s2cid=202096365 |oclc=1083673357 |lccn=2019003170}}</ref><ref name="Nobel">{{cite web |last=Klebs |first=Florian |date=December 17, 2001 |title=Deutschland – Wiege des Nobelpreis: Tourismus-Industrie und Forschung auf den Spuren Alfred Nobels |url=https://www.humboldt-foundation.de/kosmos/kultur/2001_002.htm |archive-url=https://web.archive.org/web/20021117030549/https://www.humboldt-foundation.de/kosmos/kultur/2001_002.htm |archive-date=November 17, 2002 |access-date=October 12, 2018 |publisher=[[Alexander von Humboldt Foundation]] |language=de}}</ref>

The extraction site on Lüneburg Heath was 1863–1994 Neuohe, while the storage sites were:
{| class="wikitable sortable"
! Storage site !! from !! to
|-
|Wiechel || 1871 || 1978
|-
|Hützel || 1876 || 1969
|-
|Hösseringen  || {{circa|1880|lk=no|sortable=yes}} || 1894
|-
|Hammerstorf || {{circa|1880|lk=no|sortable=yes}} || 1920
|-
|Oberohe || 1884 || 1970
|-
|Schmarbeck || 1896 || {{circa|1925|lk=no|sortable=yes}}
|-
|Steinbeck || 1897 || 1928
|-
|Breloh || 1907 || 1975
|-
|Schwindebeck || 1913 || 1973
|-
|Hetendorf || 1970 || 1994
|}

The [[Lagerstätte|deposits]] are up to {{convert|28|m||sp=us}} thick and are all of freshwater diatomaceous earth.{{citation needed|date=April 2021}}

<gallery mode="packed">
File:KieselgurNeuohe4-2.jpg|{{circa|1900}}–1910 Diatomaceous earth pit at Neuohe
File:KieselgurNeuohe3-2.jpg|{{circa|1900}}–1910 a drying area: One firing pile is being prepared; another is under way.
File:KieselgurNeuohe2-2.jpg|1913: Staff at the Neuohe factory, with male workers and a female cook in front of a drying shed
</gallery>

Until [[World War I]], almost the entire worldwide production of diatomaceous earth was from this region.{{citation needed|date=April 2021}}

== Other deposits ==
In Poland diatomaceous earth deposits are found in Jawornik, and are composed mostly of diatomaceous skeletons (frustules).<ref>{{Cite journal |last1=Lutyński |first1=Marcin |last2=Sakiewicz |first2=Piotr |last3=Lutyńska |first3=Sylwia |date=October 31, 2019 |title=Characterization of Diatomaceous Earth and Halloysite Resources of Poland |journal=Minerals |volume=9 |issue=11 |pages=670 |doi=10.3390/min9110670 |bibcode=2019Mine....9..670L |doi-access=free}}</ref>

In Germany, diatomaceous earth was also extracted at [[Altenschlirf]]<ref>{{cite web |title=Was ist es um die Kieselgur? |url=https://www2.natpa.de/bonifatius/senken/p7.htm |url-status=dead |archive-url=https://web.archive.org/web/20070928020701/https://www2.natpa.de/bonifatius/senken/p7.htm |archive-date=September 28, 2007 |access-date=March 10, 2010 |language=de}} Über den früheren Abbau von Kieselgur im Vogelsberg/Hessen.</ref> on the [[Vogelsberg]] ([[Upper Hesse]]) and at [[Klieken]]<ref>[https://homepages.compuserve.de/tmby100/kieselgur.htm Geschichte des Kieselgurabbaus in Klieken]. {{webarchive|url=https://web.archive.org/web/20080420063824/https://homepages.compuserve.de/tmby100/kieselgur.htm|date=April 20, 2008}}.</ref> ([[Saxony-Anhalt]]).

There is a layer of diatomaceous earth more than {{convert|6|m|ft|sp=us}} thick in the nature reserve of [[Soos (Nature reservation)|Soos]] in the Czech Republic.<ref name="SoosRef">{{cite web | url=https://drusop.nature.cz/ost/archiv/plany_pece/index.php?frame&ID=26651 | title=Protokol o vypořádání připomínek a schválení plánu péče NPR Soos na období 2016–2023 | trans-title=Protocol on the settlement of comments and approval of the NPR Soos care plan for the period 2016-2023 | publisher=Ministerstvo životního prostředí [Ministry of the Environment] | date=February 1, 2016 | access-date=April 5, 2021 | page=13 | language=Czech}}</ref>

Deposits on the [[Isle of Skye]], off the west coast of Scotland, were mined until 1960.<ref>{{cite web |url=https://www.stornowaygazette.co.uk/news/skye-diatomite-a-lost-industry-1-118249 |title=Skye diatomite: A lost industry |website=www.stornowaygazette.co.uk |access-date=January 5, 2019 |archive-date=January 6, 2019 |archive-url=https://web.archive.org/web/20190106055145/https://www.stornowaygazette.co.uk/news/skye-diatomite-a-lost-industry-1-118249 |url-status=dead }}</ref>

In [[Colorado]] and in [[Clark County, Nevada]], United States, there are deposits that are up to several hundred meters thick in places. Marine deposits have been worked in the [[Sisquoc Formation]] in [[Santa Barbara County, California]] near [[Lompoc, California|Lompoc]] and along the [[Southern California]] [[coast]]. This is the world's largest deposit of diatomite.<ref>{{cite magazine |last=Rice |first=Stanley |date=July–August 2020 |title=Creationist Funhouse, Episode Four: God Plays In The Mud |url=https://skepticalinquirer.org/2020/06/creationist-funhouse-episode-four-god-plays-in-the-mud/ |url-status= |magazine=[[Skeptical Inquirer]] |location=Amherst, New York |publisher=[[Center for Inquiry]] |archive-url=https://web.archive.org/web/20210304161021/https://skepticalinquirer.org/2020/06/creationist-funhouse-episode-four-god-plays-in-the-mud/ |archive-date=March 4, 2021 |access-date=March 4, 2021}}</ref> Additional marine deposits have been worked in [[Maryland]], [[Virginia]], [[Algeria]] and the [[MoClay]] of Denmark. Freshwater lake deposits occur in Nevada, [[Oregon]], [[Washington (state)|Washington]] and [[California]]. Lake deposits also occur in [[interglacial]] lakes in the eastern United States, in Canada and in Europe in Germany, France, Denmark and the Czech Republic. The worldwide association of diatomite deposits and [[volcanic]] deposits suggests that the availability of silica from [[volcanic ash]] may be necessary for thick diatomite deposits.<ref name=AIME/>

Diatomaceous earth is sometimes found on [[desert]] surfaces. Research has shown that the erosion of diatomaceous earth in such areas (such as the [[Bodélé Depression]] in the [[Sahara]]) is one of the most important sources of climate-affecting dust in the atmosphere.<ref>{{cite journal |last1=Todd |first1=Martin C. |last2=Washington |first2=Richard |last3=Martins |first3=José Vanderlei |last4=Dubovik |first4=Oleg |last5=Lizcano |first5=Gil |last6=M'Bainayel |first6=Samuel |last7=Engelstaedter |first7=Sebastian |title=Mineral dust emission from the Bodélé Depression, northern Chad, during BoDEx 2005 |journal=Journal of Geophysical Research |date=March 22, 2007 |volume=112 |issue=D6 |pages=D06207 |doi=10.1029/2006JD007170|bibcode=2007JGRD..112.6207T |doi-access=free }}</ref>

The siliceous [[frustule]]s of [[diatom]]s accumulate in fresh and brackish wetlands and lakes. Some peats and mucks contain a sufficient abundance of frustules such that they can be mined. Most of Florida's diatomaceous earths have been found in the muck of wetlands or lakes. The American Diatomite Corporation, from 1935 to 1946, refined a maximum of 145 tons per year from their processing plant near [[Clermont, Florida]]. Muck from several locations in [[Lake County, Florida]] was dried and burned ([[calcined]]) to produce the diatomaceous earth.<ref>{{cite book | first=John H. Jr. | last=Davis |title=The Peat Deposits of Florida Their Occurrence, Development and Uses, Geological Bulletin No. 30. |publisher=Florida Geological Survey |year=1946}}</ref>

It was formerly extracted from Lake [[Mývatn]] in Iceland.

The commercial deposits of diatomite are restricted to [[Tertiary]] or [[Quaternary]] periods. Older deposits from as early as the [[Cretaceous]] Period are known, but are of low quality.<ref name=AIME>Cummins, Arthur B., ''Diatomite'', in ''Industrial Minerals and Rocks'', 3rd ed. 1960, [[American Institute of Mining, Metallurgical, and Petroleum Engineers]], pp. 303–319</ref>

Diatomite deposits rich in fossils have been located in New Zealand, but mining of the [[Foulden Maar]] deposits on an industrial scale, for conversion to animal feed, has drawn strong opposition.<ref>{{cite news|last1=Hancock|first1=Farah|date=May 13, 2019|title=Opposition grows to fossil mining|work=|agency=Newsroom.co.nz|url=https://www.newsroom.co.nz/2019/05/13/581997/growing-opposition-to-fossil-mining|access-date=January 21, 2021}}</ref>

== Commercial form ==
Diatomaceous earth is available commercially in several formats:
* [[granulated]] diatomaceous earth is a raw material simply crushed for convenient packaging
* [[Mill (grinding)|milled]] or [[micronized]] diatomaceous earth is especially fine (10&nbsp;μm to 50&nbsp;μm) and used for insecticides
* [[calcined]] diatomaceous earth is heat-treated and activated for filters

[[File:Diatomaceous earth closeup 2001-10-18.jpg|thumb|right|Individual diatom cell walls often maintain their shape even in commercially processed filter media, such as this one for swimming pools.]]
[[File:Diatoms through the microscope.jpg|thumb|Live marine diatoms from Antarctica (magnified)]]

== Usage ==
=== Explosives ===
In 1866, [[Alfred Nobel]] discovered that [[nitroglycerin]] could be made more stable if absorbed in diatomite (''kieselguhr'' in German).<ref>{{Cite web |title=Nitroglycerine and Dynamite |url=https://www.nobelprize.org/alfred-nobel/nitroglycerine-and-dynamite/ |access-date=November 27, 2023 |website=NobelPrize.org |date=June 11, 2013 |language=en-US}}</ref> This allowed safer transport and handling than pure nitroglycerin in liquid form. Nobel patented this mixture as [[dynamite]] in 1867; the mixture is also called guhr dynamite in reference to the kieselguhr.<ref>{{cite book |last=Rustan |first=Agne |title=Rock Blasting Terms and Symbols: A Dictionary of Symbols and Terms in Rock Blasting and Related Areas like Drilling, Mining and Rock Mechanics |url=https://books.google.com/books?id=S0FZDwAAQBAJ&q=guhr&pg=PA83 |date=February 1, 1998 |publisher=Taylor & Francis |isbn=978-1-4665-7178-5 |page=83}}</ref><ref>{{cite book |last=Bulson |first=P.S. |title=Explosive Loading of Engineering Structures |url=https://books.google.com/books?id=U02uDwAAQBAJ&q=guhr&pg=PA3 |date=July 24, 1997 |publisher=CRC Press |isbn=978-1-135-82980-3 |page=3}}</ref>

=== Filtration ===
The [[Celle]] engineer, Wilhelm Berkefeld, recognized the ability of the diatomaceous earth to filter and developed tubular filters (known as filter candles) fired from diatomaceous earth.<ref>{{cite web|url=https://technomaps.veoliawatertechnologies.com/berkefeld-aquantis/en/|title=Berkefeld & Aquantis Water Treatment – Veolia Water Technologies|website=technomaps.veoliawatertechnologies.com|access-date=February 19, 2022|archive-date=February 27, 2021|archive-url=https://web.archive.org/web/20210227064531/http://technomaps.veoliawatertechnologies.com/berkefeld-aquantis/en/|url-status=dead}}</ref> During the [[cholera]] [[epidemic]] in [[Hamburg]] in 1892, these [[Berkefeld filter]]s were used successfully.

One form of diatomaceous earth is used as a [[Filtration|filter]] medium, especially for swimming pools. It has a high porosity because it is composed of microscopically small, hollow particles. Diatomaceous earth (sometimes referred to by trademarked brand names such as Celite) is used in chemistry as a filtration aid, to increase flow rate, and filter very fine particles that would otherwise pass through or clog [[filter paper]]. It is also used to filter water, particularly in the drinking water treatment process and in [[aquarium|fish tanks]], and other liquids, such as beer and wine. It can also filter syrups, sugar, and honey without removing or altering their color, taste, or nutritional properties.<ref name="RootRoot2005">{{cite book |author1=Root |first=Amos Ives |url=https://books.google.com/books?id=i0PoSYNEsh0C&pg=PA387 |title=The ABC And Xyz of Bee Culture |author2=Root |first2=Ernest Rob |date=March 1, 2005 |publisher=Kessinger Publishing |isbn=978-1-4179-2427-1 |page=387}}{{Dead link|date=January 2024|bot=InternetArchiveBot|fix-attempted=yes}}</ref>

=== Abrasive ===
The oldest use of diatomite is as a very mild abrasive and has been used in [[toothpaste]], metal [[Polishing|polishes]], and some facial scrubs.

=== Pest control ===
Diatomite is of value as an [[insecticide]] because of its abrasive and physico-[[sorptivity|sorptive]] properties.<ref>{{cite conference|url= https://assets.publishing.service.gov.uk/media/57a08d31e5274a31e00016d2/R8179030405.pdf |title= Standardized testing for diatomaceous earth |last1= Fields |first1= Paul |last2= Allen |first2= Sylvia |first3= Zlatko |last3= Korunic |first4= Alan |last4= McLaughlin |first5= Tanya |last5= Stathers |date= July 2002 |publisher= Entomological Society of Manitoba |book-title= Proceedings of the Eighth International Working Conference of Stored-Product Protection |location= York, U.K. }}</ref> The fine powder [[adsorption|adsorbs]] [[lipid]]s from the waxy outer layer of the [[exoskeleton]]s of many species of insects; this layer acts as a barrier that resists the loss of water vapour from the insect's body. Damaging the layer increases the evaporation of water from their bodies, so that they dehydrate, often fatally.

This also works against [[gastropod]]s and is commonly employed in gardening to defeat [[slug]]s.<ref>{{cite web |title=Using Diatomaceous Earth for Slugs |url=https://www.slugcuisine.co.uk/diatomaceous-earth/ |website=Slug Cuisine}}</ref> However, since slugs inhabit humid environments, efficacy is low. Diatomaceous earth is sometimes mixed with an attractant or other additives to increase its effectiveness.

The shape of the diatoms contained in a deposit has not been proven to affect their functionality when it comes to the adsorption of lipids; however, certain applications, such as that for slugs and snails, work best when a particularly shaped diatom is used, suggesting that lipid adsorption is not the only factor involved. For example, in the case of slugs and snails, large, spiny diatoms work best to lacerate the epithelium of the mollusk. Diatom shells will work to some degree on the vast majority of animals that undergo [[ecdysis]] in shedding [[cuticle]], such as [[arthropod]]s or [[nematode]]s. It also may have other effects on [[lophotrochozoa]]ns, such as [[mollusk]]s or [[annelid]]s.

[[Medical-grade]] diatomite has been studied for its efficacy as a [[deworming]] agent in cattle; in both studies cited the groups being treated with diatomaceous earth did not fare any better than control groups.<ref name="Lartigue 2004 660–674">{{cite journal |last1=Lartigue |first1=E. del C. |last2=Rossanigo |first2=C. E. |year=2004 |title=Insecticide and anthelmintic assessment of diatomaceous earth in cattle |journal=Veterinaria Argentina |volume=21 |issue=209 |pages=660–674 }}</ref><ref name="Fernandez 1998 635–641">{{cite journal |last1=Fernandez |first1=M. I. |last2=Woodward |first2=B. W. |last3=Stromberg |first3=B. E. |year=1998 |title=Effect of diatomaceous earth as an anthelmintic treatment on internal parasites and feedlot performance of beef steers |journal=Animal Science |volume=66 |issue=3 |pages=635–641 |doi=10.1017/S1357729800009206 }}</ref> It is commonly used in lieu of [[boric acid]] and can be used to help control and possibly eliminate [[Cimex|bed bugs]],<ref>{{Cite web |date=October 29, 2020 |title=Bed Bug Control With Diatomaceous Earth |url=https://www.absorbentproductsltd.com/bed-bug-control-with-diatomaceous-earth/ |access-date=October 29, 2020 |website=Absorbent Products |archive-date=November 4, 2020 |archive-url=https://web.archive.org/web/20201104022609/https://www.absorbentproductsltd.com/bed-bug-control-with-diatomaceous-earth/ |url-status=dead }}</ref> [[house dust mite]], [[cockroach]], [[ant]], and [[flea]] infestations.<ref name="Faulde">{{cite journal |first1=M. K. |last1=Faulde |first2=M. |last2=Tisch |first3=J. J. |last3=Scharninghausen |title=Efficacy of modified diatomaceous earth on different cockroach species (Orthoptera, Blattellidae) and silverfish (Thysanura, Lepismatidae) |journal=Journal of Pest Science |date=August 2006 |volume=79 |issue=3 |pages=155–161 |doi=10.1007/s10340-006-0127-8 |bibcode=2006JPesS..79..155F |s2cid=39203675 }}</ref>

Diatomaceous earth is widely applied for insect control in grain storage.<ref>{{cite web |url=https://www.diatomaceousearth.com/blogs/learning-center/diatomaceous-earth-protect-food-storage |title=Diatomaceous Earth: Protect Food Storage|date=January 23, 2018 |publisher=diatomaceousearth.com |access-date=March 8, 2020}}</ref> It is used to control cannibalistic behaviors in [[confused flour beetle]]s, which infest flour storages.

In order to be effective as an insecticide, diatomaceous earth must be [[calcination|uncalcinated]] (i.e., it must not be heat-treated prior to application)<ref>{{Cite book|title=Encyclopedia of Entomology|last=Capinera|first=John L.|editor1-last=Capinera|editor1-first=John L.|edition=Second|year=2008|page=1216|chapter=Diatomaceous earth|publisher=Springer|chapter-url=https://books.google.com/books?id=i9ITMiiohVQC|isbn=978-1-4020-6242-1}}</ref>{{Better source needed|reason=This secondary source implies the claim, but doesn't explicitly state it, and it lacks supporting explanations and inline citations. Action: verify references in secondary source.|date=October 2024}} and have a mean particle size below about 12&nbsp;μm (i.e., food grade—[[#Specific varieties|see below]]).{{Citation needed|date=October 2024}}

Although considered to be relatively low-risk, pesticides containing diatomaceous earth are not exempt from regulation in the United States under the [[Federal Insecticide, Fungicide, and Rodenticide Act]] and must be registered with the [[Environmental Protection Agency]].<ref>{{cite web |title=Pesticide Labeling Questions & Answers – Advertising Claims |url=https://www.epa.gov/pesticides/regulating/labels/labels_faq/lr_faq_1.html |url-status=dead |archive-url=https://web.archive.org/web/20130530143625/https://www.epa.gov/pesticides/regulating/labels/labels_faq/lr_faq_1.html |archive-date=May 30, 2013 |access-date=July 7, 2013 |publisher=[[United States Environmental Protection Agency|EPA]]}}</ref>

=== Thermal ===
Its thermal properties enable it to be used as the barrier material in some fire-resistant safes.{{Citation needed|date=March 2013}} It is also used in evacuated powder insulation for use with cryogenics.<ref>Flynn, Thomas M. "Cryogenic Equipment and Cryogenic Systems Analysis." Cryogenic Engineering. Boca Raton etc.: CRC, 2005. Print.</ref> Diatomaceous earth powder is inserted into the vacuum space to aid in the effectiveness of vacuum insulation. It was used in the classical [[AGA cooker]]s as a thermal heat barrier.{{citation needed|date=July 2023}}

=== Catalyst support ===
Diatomaceous earth also finds some use as a [[Catalyst support|support]] for [[catalyst]]s, generally serving to maximize a catalyst's [[surface area]] and [[Activity (chemistry)|activity]]. For example, [[nickel]] can be supported on the material—the combination is called Ni–Kieselguhr—to improve its activity as a [[hydrogenation]] catalyst.<ref>{{cite book|last1=Nishimura|first1=Shigeo|title=Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis|date=2001|publisher=Wiley-Interscience|location=New York|isbn=9780471396987|pages=2–5|edition=1st|url=https://books.google.com/books?id=RjZRAAAAMAAJ}}</ref>

=== Agriculture ===
Natural freshwater diatomaceous earth is used in agriculture for grain storage as an [[anticaking agent]], as well as an insecticide.<ref>{{cite web |url=https://www.gov.mb.ca/agriculture/crops/cropproduction/faa06s00.html |title=Prevention and Management of Insects and Mites in Farm-Stored Grain |publisher=Province of Manitoba |access-date=July 7, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131018021402/https://www.gov.mb.ca/agriculture/crops/cropproduction/faa06s00.html |archive-date=October 18, 2013}}</ref> It is approved by the U.S. Food and Drug Administration as a [[feed additive]]<ref name="FDA1">{{cite web |date=April 1, 2001 |title=21 CFR 573.340 – Diatomaceous earth |url=https://www.gpo.gov/fdsys/pkg/CFR-2001-title21-vol6/pdf/CFR-2001-title21-vol6-sec573-340.pdf |access-date=February 9, 2016 |work=Code of Federal Regulations (annual edition)—Title 21 – Food and Drugs—Part 573 – Food additives permitted in feed and drinking water of animals—Section 573.340 – Diatomaceous earth |publisher=[[Food and Drug Administration]]/U.S. Government Publishing Office}}</ref> to prevent [[caking]].<ref>{{Cite web |title=Diatomaceous Earth – How To Rid Bed Bugs Naturally – Organic |url=https://www.fertilizeronline.com/diato-earth.php |access-date=April 17, 2022 |website=www.fertilizeronline.com}}</ref>

Some believe it may be used as a natural [[anthelmintic]] (dewormer), although studies have not shown it to be effective.<ref name="Lartigue 2004 660–674"/><ref name="Fernandez 1998 635–641"/> Some farmers add it to their livestock and [[Chicken|poultry]] feed to prevent the caking of feed.<ref name="usdade">{{cite web|url=https://www.sgggc.org/insect-management-food-processing-facilities-heat-diatomaceous-earth/|title=Diatomaceous Earth (DE)|date=January 15, 2024 }}</ref> "Food-Grade Diatomaceous Earth" is widely available in agricultural feed supply stores.

Freshwater diatomite can be used as a growing medium in [[hydroponic]] gardens.

It is also used as a growing medium in potted plants, particularly as [[bonsai]] soil. Bonsai enthusiasts use it as a soil additive, or pot a bonsai tree in 100% diatomaceous earth. In vegetable gardening it is sometimes used as a [[soil conditioner]], because like [[perlite]], [[vermiculite]], and [[Expanded clay aggregate|expanded clay]], it retains water and nutrients, while draining fast and freely, allowing high oxygen circulation within the growing medium.

=== Marker in livestock nutrition experiments ===
[[File:Diatomaceous Earth.jpg|thumb|A sample of food-grade diatomaceous earth]]
Natural dried, not calcinated diatomaceous earth is regularly used in livestock nutrition research as a source of acid-insoluble ash (AIA), which is used as an indigestible marker. By measuring the content of AIA relative to nutrients in test diets and feces or digesta sampled from the terminal ileum (last third of the small intestine) the percentage of that nutrient digested can be calculated using the following equation:

{{block indent|<math>N = \left ( 1 - \frac{N_f}{N_F} \times \frac{A_F}{A_f} \right ) \times 100 </math>}}

where:
{{block indent|N is the nutrient digestibility (%)}}
{{block indent|N<sub>f</sub> is the amount of nutrients in the feces (%)}}
{{block indent|N<sub>F</sub> is the amount of nutrients in the feed (%)}}
{{block indent|A<sub>f</sub> is the amount of AIA in the feces (%)}}
{{block indent|A<sub>F</sub> is the amount of AIA in the feed (%)}}

Natural freshwater diatomaceous earth is preferred by many researchers over chromic oxide, which has been widely used for the same purpose, the latter being a known carcinogen and, therefore, a potential hazard to research personnel.

=== Construction ===
Spent diatomaceous earth from the [[brewing]] process can be added to ceramic mass for the production of red bricks with higher open porosity.<ref>{{cite journal | last1 = Ferraz | first1 = E. | last2 = Coroado | first2 = J. | last3 = Silva | first3 = J. | last4 = Gomes | first4 = C. | last5 = Rocha | first5 = F. | year = 2011 | title = Manufacture of ceramic bricks using recycled brewing spent kieselguhr | journal = Materials and Manufacturing Processes | volume = 26 | issue = 10| pages = 1319–1329 | doi = 10.1080/10426914.2011.551908| s2cid = 135734681 }}</ref>

Diatomaceous earth is considered a prominent inorganic non-metallic material that can be used for the production of various ceramics, including production of porous ceramics under low temperature hydrothermal technology.<ref>{{cite journal |last1=Reka |first1=Arianit A. |last2=Pavlovski |first2=Blagoj |last3=Makreski |first3=Petre |title=New optimized method for low-temperature hydrothermal production of porous ceramics using diatomaceous earth |journal=Ceramics International |date=October 2017 |volume=43 |issue=15 |pages=12572–12578 |doi=10.1016/j.ceramint.2017.06.132 |url=https://www.academia.edu/34164748}}</ref>

=== Home goods ===

Diatomaceous earth (DE) is used in some home products where dryness or the ability to wick away moisture is needed. In particular there are bath mats made of DE which absorb water from the bather and allow it to spread the material and rapidly evaporate. There are also spoons made of DE for scooping sugar and other hydroscopic kitchen ingredients.

== Specific varieties ==
* '''Tripolite''' is the variety found in [[Tripoli, Libya]].
* '''Bann clay''' is the variety found in the [[Lower Bann]] valley in Northern Ireland.
* ''Moler'' ([[Fur Formation|mo-clay]]) is the variety found in northwestern Denmark, especially on the islands of [[Fur (island)|Fur]] and [[Mors (island)|Mors]].
* ''Freshwater-derived food grade'' diatomaceous earth is the type used in United States agriculture for grain storage, as feed supplement, and as an insecticide. It is produced [[calcination|uncalcinated]], has a very fine particle size, and is very low in crystal silica (<2%).
* ''Salt-water-derived pool / beer / wine filter grade'' is not suitable for human consumption or effective as an insecticide. Usually [[calcinated]] before being sold to remove impurities and undesirable volatile contents, it is composed of larger particles than the freshwater version and has a high crystalline silica content (>60%).

== Microbial degradation ==
Certain species of bacteria in oceans and lakes can accelerate the rate of dissolution of silica in dead and living diatoms by using [[hydrolytic]] enzymes to break down the organic algal material.<ref>{{cite journal |last1=Bidle |first1=Kay D. |last2=Azam |first2=Farooq |title=Accelerated dissolution of diatom silica by marine bacterial assemblages |journal=Nature |date=February 1999 |volume=397 |issue=6719 |pages=508–512 |doi=10.1038/17351 |bibcode=1999Natur.397..508B |s2cid=4397909 }}</ref><ref>{{cite journal |last1=Zakharova |first1=Yulia R. |last2=Galachyants |first2=Yuri P. |last3=Kurilkina |first3=Maria I. |last4=Likhoshvay |first4=Alexander V. |last5=Petrova |first5=Darya P. |last6=Shishlyannikov |first6=Sergey M. |last7=Ravin |first7=Nikolai V. |last8=Mardanov |first8=Andrey V. |last9=Beletsky |first9=Alexey V. |last10=Likhoshway |first10=Yelena V. |last11=Mormile |first11=Melanie R. |title=The Structure of Microbial Community and Degradation of Diatoms in the Deep Near-Bottom Layer of Lake Baikal |journal=PLOS ONE |date=April 1, 2013 |volume=8 |issue=4 |pages=e59977 |doi=10.1371/journal.pone.0059977 |pmid=23560063 |pmc=3613400 |bibcode=2013PLoSO...859977Z |doi-access=free }}</ref>

== Climatologic importance ==
The Earth's [[climate]] is affected by [[dust]] in the [[atmosphere]], so locating major sources of atmospheric dust is important for [[climatology]]. Research indicates that surface deposits of diatomaceous earth play an important role. Research shows that significant dust comes from the [[Bodélé Depression]] in [[Chad]], where storms push diatomite gravel over [[dune]]s, generating dust by [[abrasion (geology)|abrasion]].<ref name="WashingtonTodd2006">{{cite journal |last1=Washington |first1=R. |last2=Todd |first2=M. C. |last3=Lizcano |first3=G. |last4=Tegen |first4=I. |last5=Flamant |first5=C. |last6=Koren |first6=I. |last7=Ginoux |first7=P. |last8=Engelstaedter |first8=S. |last9=Bristow |first9=C. S. |last10=Zender |first10=C. S. |last11=Goudie |first11=A. S. |last12=Warren |first12=A. |last13=Prospero |first13=J. M. |title=Links between topography, wind, deflation, lakes and dust: The case of the Bodélé Depression, Chad |journal=Geophysical Research Letters |volume=33 |issue=9 |pages=L09401 |year=2006|doi=10.1029/2006GL025827 |bibcode=2006GeoRL..33.9401W|s2cid=14122607 |display-authors=5|url=https://discovery.ucl.ac.uk/40693/1/2006GL025827.pdf }}</ref>

== Safety considerations ==
Inhalation of ''crystalline'' silica harms the lungs, causing [[silicosis]]. ''Amorphous'' silica is considered to have low toxicity, but prolonged inhalation causes lung changes.<ref>{{cite web|url=https://www.cdc.gov/niosh/pel88/68855-54.html|title=NIOSH 1988 OSHA PEL Project Documentation: List by Chemical Name: SILICA, AMORPHO|date=September 19, 2018|publisher=CDC}}</ref> Diatomaceous earth is mainly [[amorphous silica]] but contains some crystalline silica, especially in the saltwater forms.<ref>{{cite web |url=https://www.spca.bc.ca/assets/documents/welfare/professional-resources/farmer-resources/diatomaceous-earth-factsheet.pdf |title=Diatomaceous Earth: Its Use and Precautions |access-date= November 9, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130717171434/https://www.spca.bc.ca/assets/documents/welfare/professional-resources/farmer-resources/diatomaceous-earth-factsheet.pdf |archive-date=July 17, 2013 }}</ref> In a 1978 study of workers, those exposed to natural diatomaceous earth for over five years had no significant lung changes while 40% of those exposed to the calcined form had developed [[pneumoconiosis]].<ref>{{cite web|url=https://www.cdc.gov/niosh/docs/81-123/pdfs/0552.pdf |date=September 1978 |title=Occupational Health Guideline for Amorphous Silica |work=[[Centers for Disease Control and Prevention|CDC]] |access-date=March 24, 2020 |url-status=live |archive-url=https://web.archive.org/web/20200312013339/https://www.cdc.gov/niosh/docs/81-123/pdfs/0552.pdf |archive-date=March 12, 2020}}</ref> Today's standard diatomaceous earth formulations are safer to use, as they are predominantly made of amorphous silica and contain little or no crystalline silica.<ref name="Inert Dusts"/>

The crystalline silica content of diatomaceous earth is regulated in the United States by the [[Occupational Safety and Health Administration]] (OSHA). There are guidelines from the [[National Institute for Occupational Safety and Health]] that set maximum amounts allowable in the product (1%) and in the air near the breathing zone of workers, with a [[recommended exposure limit]] at 6 mg/m<sup>3</sup> over an 8-hour workday.<ref name="Inert Dusts">{{cite web|url=https://www.oznet.ksu.edu/grsc_subi/Teaching/GRSC651/GRSC651_Courses_Material/lecture_slides/GRSC651_lect_20(1)_Inert_Dusts.pdf|date=July 10, 2003|title=Inert Dusts|author1=Bhadriraju Subramanyam|author2=Rennie Roesli|archive-url=https://web.archive.org/web/20030710215341/https://www.oznet.ksu.edu/grsc_subi/Teaching/GRSC651/GRSC651_Courses_Material/lecture_slides/GRSC651_lect_20(1)_Inert_Dusts.pdf|archive-date=July 10, 2003}}</ref> OSHA has set a [[permissible exposure limit]] for diatomaceous earth as 20 mppcf (80 mg/m<sup>3</sup>/%SiO<sub>2</sub>). At levels of 3,000 mg/m<sup>3</sup>, diatomaceous earth is immediately dangerous to life and health.<ref>{{Cite web|title = NIOSH Pocket Guide to Chemical Hazards – Silica, amorphous|url = https://www.cdc.gov/niosh/npg/npgd0552.html|publisher=CDC|access-date = November 21, 2015}}</ref>

In the 1930s, workers with long-term occupational exposure in the [[cristobalite]] diatomaceous earth industry who were exposed to high levels of airborne crystalline silica over decades were found to have an increased risk of [[silicosis]].<ref name="HughesWeill1998">{{cite journal |last1=Hughes |first1=Janet M. |last2=Weill |first2=Hans |last3=Checkoway |first3=Harvey |last4=Jones |first4=Robert N. |last5=Henry |first5=Melanie M. |last6=Heyer |first6=Nicholas J. |last7=Seixas |first7=Noah S. |last8=Demers |first8=Paul A. |title=Radiographic Evidence of Silicosis Risk in the Diatomaceous Earth Industry |journal=American Journal of Respiratory and Critical Care Medicine |volume=158 |issue=3 |year=1998 |pages=807–814 |doi=10.1164/ajrccm.158.3.9709103 |pmid=9731009}}</ref>

Diatomite produced for pool filters is treated with high heat ([[calcination]]) and a fluxing agent ([[soda ash]]), causing the formerly harmless amorphous silicon dioxide to assume its crystalline form.<ref name="Inert Dusts"/>

== See also ==
* {{annotated link|Aerogel}}
* {{annotated link|Biomineralization}}
* {{annotated link|Fuller's earth}}
* {{annotated link|Perlite}}
* {{annotated link|Rock flour}}
* {{annotated link|Siliceous ooze}}
* {{annotated link|Zeolite}}

== References ==
{{Reflist|30em}}

== External links ==
* {{ICSC|0248|02}}
* [https://www.cdc.gov/niosh/npg/npgd0552.html CDC – NIOSH Pocket Guide to Chemical Hazards]
* [https://minerals.usgs.gov/minerals/pubs/commodity/diatomite/ Diatomite: Statistics and Information – USGS]
* [https://www.mindat.org/min-9855.html Tripolite: Tripolite mineral data] Citat: "...A diatomaceous earth consisting of opaline silica..."
* [https://www.eap.mcgill.ca/publications/eap4.htm Diatomaceous Earth: A Non Toxic Pesticide]
{{Rock type}}
{{Authority control}}

{{DEFAULTSORT:Diatomaceous Earth}}
[[Category:Sedimentary rocks]]
[[Category:Inorganic insecticides]]
[[Category:Swimming pools]]
[[Category:Water treatment]]
[[Category:Soil]]
[[Category:Soil improvers]]
[[Category:Fodder]]
[[Category:Microfossils]]
[[Category:Biomineralization]]
[[Category:Industrial minerals]]
[[Category:Sustainable agriculture]]