Editing Chalk (section)

==Uses==
[[File:Colored chalks (3391214973).jpg|thumb|Chalk in different colors]]
[[File:Chalk-Sidewalk-Art-0092.jpg|thumb|right|Child drawing with [[sidewalk chalk]]]]
Most people first encounter chalk in school where it refers to [[Blackboard|blackboard chalk]], which was originally made of mineral chalk, since it readily crumbles and leaves particles that stick loosely to rough surfaces, allowing it to make writing that can be readily erased. Blackboard chalk manufacturers now may use mineral chalk, other [[limestone|mineral sources]] of calcium carbonate, or the mineral [[gypsum]] ([[calcium sulfate]]). While gypsum-based blackboard chalk is the lowest cost to produce, and thus widely used in the [[developing world]], use of carbonate-based chalk produces larger particles and thus less dust, and it is marketed as "dustless chalk".<ref>Thakker, M., Shukla, P. and Shah, D.O., 2015. Surface and colloidal properties of chalks: A novel approach using surfactants to convert normal chalks into dustless chalks. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 480, pp.&nbsp;236–244. [[doi:10.1016/j.colsurfa.2015.01.054]]</ref><ref name=geology/>

Coloured chalks, pastel chalks, and [[sidewalk chalk]] (shaped into larger sticks and often coloured), used to draw on [[sidewalk]]s, streets, and [[driveway]]s, are primarily made of gypsum rather than calcium carbonate chalk.<ref>{{cite web|url=http://www.madehow.com/Volume-1/Chalk.html|title=How chalk is made - material, making, used, processing, procedure, product, industry|website=www.madehow.com|url-status=live|archive-url=https://web.archive.org/web/20171103073723/http://www.madehow.com/Volume-1/Chalk.html|archive-date=2017-11-03}}</ref>
[[File:Hojer jan 0429.JPG|thumb|Climber [[Jan Hojer]] blows surplus chalk from his hand.]]

[[Magnesium carbonate]] chalk is commonly used as a drying agent to obtain better grip by gymnasts and rock climbers.

Glazing [[putty]] mainly contains chalk as a filler in [[linseed oil]].<ref>{{cite book |last1=Rohleder |first1=Johannes |chapter=The beginnings: Calcium carbonate in glazing putty and rubber |title=Calcium Carbonate |date=2001 |pages=138–159 |doi=10.1007/978-3-0348-8245-3_6|isbn=978-3-0348-9490-6 }}</ref>

Chalk and other forms of limestone may be used for their properties as a [[base (chemistry)|base]].{{sfn|Blatt|Middleton|Murray|1980|p=445}} Chalk is a source of [[quicklime]] by [[thermal decomposition]], or [[slaked lime]] following [[quenching]] of quicklime with water.<ref>{{cite book|last=Blount|first=Bertram|title=Chemistry for Engineers and Manufacturers: Chemistry of manufacturing processes|year=1990|publisher=University of Wisconsin – Madison|url=https://books.google.com/books?id=Z-vmAAAAMAAJ&q=chalk+manufacturing&pg=PA127}}</ref> In [[agriculture]], chalk is used for raising [[pH]] in soils with high [[acidity]].<ref name="Oates2008">{{cite book|first=J. A. H.|last=Oates|title=Lime and Limestone: Chemistry and Technology, Production and Uses|url=https://books.google.com/books?id=MVoEMNI5Vb0C&pg=PA111|date=11 July 2008|publisher=[[John Wiley & Sons]]|isbn=978-3-527-61201-7|pages=111–3}}</ref> Small doses of chalk can also be used as an [[antacid]].<ref>{{cite journal |last1=Clayman |first1=Charles B. |title=The Carbonate Affair: Chalk One Up |journal=JAMA: The Journal of the American Medical Association |date=5 December 1980 |volume=244 |issue=22 |pages=2554 |doi=10.1001/jama.1980.03310220052030|pmid=7431595 }}</ref> Additionally, the small particles of chalk make it a substance ideal for cleaning and polishing. For example, toothpaste commonly contains small amounts of chalk, which serves as a mild [[abrasive]].<ref>{{cite journal |last1=Baxter |first1=P. M. |last2=Davis |first2=W. B. |last3=Jackson |first3=J. |title=Toothpaste abrasive requirements to control naturally stained pellicle.: The relation of cleaning power to toothpaste abrasivity |journal=Journal of Oral Rehabilitation |date=January 1981 |volume=8 |issue=1 |pages=19–26 |doi=10.1111/j.1365-2842.1981.tb00471.x|pmid=6935391 }}</ref> Polishing chalk is chalk prepared with a carefully controlled grain size, for very fine polishing of metals.<ref>[http://chestofbooks.com/home-improvement/workshop/Workshop-Companion/Polishing-Powders.html Information on polishing powders] {{webarchive|url=http://archive.wikiwix.com/cache/20111104135738/http://chestofbooks.com/home-improvement/workshop/Workshop-Companion/Polishing-Powders.html |date=2011-11-04 }}, from the 1879 book "The Workshop Companion"</ref>

French chalk (also known as tailor's chalk) is traditionally a hard chalk used to make temporary markings on cloth, mainly by [[tailor]]s. It is now usually made of [[talc]] (magnesium silicate).<ref>{{cite conference |last1=Kumar |first1=Sublania Harish |last2=J. |first2=Singh K. |last3=K. |first3=Somani A. |title=Estimatation of talc properties after milling |conference=International Conference on Condensed Matter and Applied Physics (Icc 2015) |series=AIP Conference Proceedings |date=2016 |volume=1728 |issue=1 |pages=020139 |doi=10.1063/1.4946190|bibcode=2016AIPC.1728b0139K }}</ref>

Chalk beds form important [[petroleum reservoir]]s in the [[North Sea]]<ref>{{cite journal |last1=Hardman |first1=R.F.P. |year=1982 |title=Chalk reservoirs of the North Sea |journal=Bulletin of the Geological Society of Denmark |volume=30 |number=3–4 |pages=119–137 |doi=10.37570/bgsd-1981-30-12 |bibcode=1982BuGSD..30..119H |s2cid=149452185 |url=https://2dgf.dk/xpdf/bull30-03-04-119-137.pdf |accessdate=27 April 2021}}</ref> and along the [[Gulf Coast]] of North America.<ref name="austin-chalk">{{cite journal |last1=Pearson |first1=Krystal |title=Geologic models and evaluation of undiscovered conventional and continuous oil and gas resources: Upper Cretaceous Austin Chalk |journal=U.S. Geological Survey Scientific Investigations Report |series=Scientific Investigations Report |date=2012 |volume=2012-5159 |page=32 |doi=10.3133/sir20125159|doi-access=free |bibcode=2012usgs.rept...32P }}</ref>

=== Previous uses ===
In southeast England, [[denehole]]s are a notable example of ancient chalk pits. Such [[bell pit]]s may also mark the sites of ancient [[flint]] mines, where the prime object was to remove flint [[nodule (geology)|nodules]] for [[stone tool]] manufacture. The surface remains at [[Cissbury]] are one such example, but perhaps the most famous is the extensive complex at [[Grimes Graves]] in [[Norfolk]].<ref>{{cite journal |last1=Sieveking |first1=G. De G. |last2=Bush |first2=P. |last3=Ferguson |first3=J. |last4=Craddock |first4=P. T. |last5=Hughes |first5=M. J. |last6=Cowell |first6=M. R. |title=Prehistoric flint mines and their identification as sources of raw material |journal=Archaeometry |date=August 1972 |volume=14 |issue=2 |pages=151–176 |doi=10.1111/j.1475-4754.1972.tb00061.x|bibcode=1972Archa..14..151S }}</ref>

Chalk was traditionally used in recreation. In field sports, such as tennis played on grass, powdered chalk was used to mark the boundary lines of the playing field or court. If a ball hits the line, a cloud of chalk or pigment dust will be visible. In recent years, powdered chalk has been replaced with [[titanium dioxide]].<ref>{{cite web |url=http://www.rsc.org/learn-chemistry/content/filerepository/CMP/00/001/020/TeacherResource%20Weightlifting.pdf?v=1356513839795 |title=Archived copy |access-date=2013-10-24 |url-status=live |archive-url=https://web.archive.org/web/20131029192539/http://www.rsc.org/learn-chemistry/content/filerepository/CMP/00/001/020/TeacherResource%20Weightlifting.pdf?v=1356513839795 |archive-date=2013-10-29 }}</ref> In gymnastics, rock-climbing, weightlifting and [[tug of war]], chalk — now usually [[magnesium carbonate]] — is applied to the hands and feet to remove perspiration and reduce slipping.<ref>{{cite journal |pmid=29541333|year=2018|last1=Bacon|first1=N. T.|last2=Ryan|first2=G. A.|last3=Wingo|first3=J. E.|last4=Richardson|first4=M. T.|last5=Pangallo|first5=T.|last6=Bishop|first6=P. A.|title=Effect of Magnesium Carbonate Use on Repeated Open-Handed and Pinch Grip Weight-Assisted Pull-Ups|journal=International Journal of Exercise Science|volume=11|issue=4|pages=479–492|doi=10.70252/VQZQ3716 |pmc=5841679}}</ref>

Chalk may also be used as a house construction material instead of [[brick]] or [[wattle and daub]]: quarried chalk was cut into blocks and used as [[ashlar]], or loose chalk was rammed into blocks and laid in mortar.<ref>{{cite book|last1=Walker|first1=Peter|title=Rammed earth: design and construction guidelines|date=2005|publisher=[[Building Research Establishment]]|location=Bracknell, England|isbn=9781860817342|page=5|display-authors=etal}}</ref><ref>{{cite book|last1=Whitaker|first1=William|title=Memoirs of the Geological Survey of Great Britain|date=1872|publisher=Longmans, Green|location=London|oclc= 2531996|page=389|volume=4}}</ref> There are still houses standing which have been constructed using chalk as the main building material. Most are pre-[[Victorian architecture|Victorian]] though a few are more recent.<ref>{{cite book|last1=Easton|first1=David|title=The Rammed Earth House|date=1996|publisher=Chelsea Green Publishing|location=White River Junction, VT|isbn=9780930031794|page=[https://archive.org/details/rammedearthhouse0000east/page/15 15]|url-access=registration|url=https://archive.org/details/rammedearthhouse0000east/page/15}}</ref>

A mixture of chalk and [[Mercury (element)|mercury]] can be used as [[fingerprint powder]]. However, because of the toxicity of the mercury, the use of such mixtures for fingerprinting was abandoned in 1967.<ref>{{cite journal |last1=Sodhi |first1=G.S. |last2=Kaur |first2=J. |title=Powder method for detecting latent fingerprints: a review |journal=Forensic Science International |date=September 2001 |volume=120 |issue=3 |pages=172–176 |doi=10.1016/S0379-0738(00)00465-5|pmid=11473799 }}</ref>