View source for Flint

{{Short description|Cryptocrystalline form of the mineral quartz}}
{{Use dmy dates|date=August 2017}}
{{About|the sedimentary rock}}{{Globalise|section|date=October 2023}}
{{Infobox rock
|name=Flint
|type=Sedimentary
|coordinates=
|image=Miorcani flint.jpg
|alt=A sample of Miorcani flint
|caption=A sample of Miorcani flint from the [[Cenomanian]] chalky marl layer of the [[Moldavian Plateau]] ({{circa|{{cvt|7.5|cm|in}}}} wide)
|composition=[[Cryptocrystalline]] [[quartz]]
}}
[[File:Flint, 9cm, 171gm.jpg|right|thumb|A piece of flint {{cvt|9-10|cm|in}} long, weighing 171&nbsp;grams]]

'''Flint''', occasionally '''flintstone''', is a [[sedimentary rock|sedimentary]] [[cryptocrystalline]] form of the [[mineral]] [[quartz]],<ref>{{WebMineral |url=http://webmineral.com/data/Quartz.shtml |title=General Quartz Information}}. {{Cite web |url=http://www.webmineral.com/data/Quartz.shtml |title=Quartz Mineral Data |access-date=4 March 2022 |archive-date=11 February 2021 |archive-url=https://web.archive.org/web/20210211042305/http://www.webmineral.com/data/Quartz.shtml |url-status=bot: unknown }} (page contains [[java applet]]s depicting 3D molecular structure)</ref><ref>{{cite web |url=http://www.quartzpage.de/flint.html |title=Flint and Chert |publisher=quartzpage.de |access-date=30 March 2008 |archive-date=12 January 2018 |archive-url=https://web.archive.org/web/20180112141503/http://www.quartzpage.de/flint.html |url-status=dead }}</ref> categorized as the variety of [[chert]] that occurs in [[chalk]] or [[marl]]y [[limestone]]. Historically, flint was widely used to make [[stone tool]]s and [[fire making|start fires]].

Flint occurs chiefly as [[nodule (geology)|nodule]]s and masses in sedimentary rocks, such as [[chalk]]s and [[limestone]]s.<ref name="Flints">[http://www.bbm.me.uk/portsdown/PH_320_Flint.htm ''The Flints from Portsdown Hill''] {{webarchive |url=https://web.archive.org/web/20071113154308/http://www.bbm.me.uk/Portsdown/PH_320_Flint.htm |date=13 November 2007}}</ref><ref>{{Cite web|url=http://www.theaaca.com/Learning_Center/flintvs.htm|archiveurl=https://web.archive.org/web/20040817115706/http://www.theaaca.com/Learning_Center/flintvs.htm|url-status=dead|title=Flint vs Chert Authentic Artefacts Collectors Assn.|archivedate=17 August 2004}}</ref> Inside the nodule, flint is usually dark grey or black, green, white, or brown in colour, and has a glassy or waxy appearance. A thin, [[oxidised]] layer on the outside of the nodules is usually different in colour, typically white and rough in texture. The nodules can often be found along [[stream]]s and [[beach]]es.

Flint breaks and chips into sharp-edged pieces, making it useful in constructing a variety of cutting tools, such as [[knife]] blades and scrapers. The use of flint to make [[stone tools]] dates back more than three million years; flint's extreme [[durability]] has made it possible to accurately date its use over this time. Flint is one of the primary materials used to define the [[Stone Age]].

During the Stone Age, access to flint was so important for survival that people would travel or trade long distances to obtain the stone. [[Grime's Graves]] was an important source of flint traded across Europe.  [[Flint Ridge State Memorial|Flint Ridge]] in [[Ohio]] was another important source of flint, and [[Indigenous peoples of the Americas|Native Americans]] extracted the flint from hundreds of quarries along the ridge. This "Ohio Flint" was traded across the eastern United States, and has been found as far west as the [[Rocky Mountains]] and south around the [[Gulf of Mexico]].<ref>{{cite web|url=https://geology.com/rocks/flint.shtml|title=Uses of Flint - Tools, weapons, fire starters, gemstones|website=geology.com|access-date=26 March 2019|archive-date=27 November 2020|archive-url=https://web.archive.org/web/20201127012303/https://geology.com/rocks/flint.shtml|url-status=live}}</ref>

When struck against [[steel]], flint will produce enough sparks to ignite a fire with the correct [[tinder]], or [[gunpowder]] used [[History of gunpowder|in weapons]], namely the [[flintlock]] [[Flintlock mechanism|firing mechanism]]. Although it has been superseded in these uses by different processes (the [[percussion cap]]), or materials ([[ferrocerium]]), "flint" has lent its name as generic term for a fire starter.

==Origin==
[[File:Silica pseudomorph after halite crystals and silicified remains of algae 6.jpg|thumb|Silicified remains of algae and silica pseudomorph after [[halite]] in flint. Pebble of Loire near [[Marcigny]], France. Image width: about 5 mm]]
The exact mode of formation of flint is not yet clear, but it is thought that it occurs as a result of chemical changes in compressed [[sedimentary rock]] formations during the process of [[diagenesis]]. One [[hypothesis]] is that a gelatinous material fills cavities in the sediment, such as holes bored by [[crustaceans]] or [[molluscs]], and that this becomes [[silicification|silicified]]. This hypothesis would explain the complex shapes of flint nodules that are found. The source of dissolved silica in the porous media could be the [[spicules of silicious sponges]] ([[demosponge]]s).<ref name=Flints/> Certain types of flint, such as that from the [[south coast of England]] and its counterpart on the French side of the [[English Channel|Channel]], contain trapped [[fossilised]] marine flora. Pieces of coral and vegetation have been found preserved inside the flint, similar to the way insects and plant parts are preserved within [[amber]]. Thin slices of the stone often reveal this effect.

[[File:flintbeach.jpg|thumb|upright|Pebble beach made up of flint nodules eroded from the nearby [[chalk]] cliffs, [[Cape Arkona]], [[Rügen]], northeast Germany]]
Flint sometimes occurs in large [[flint field]]s in [[Jurassic]] or [[Cretaceous]] beds, for example, in Europe. Puzzling giant flint formations known as [[paramoudra]] and flint circles are found around Europe, but especially in [[Norfolk]], England, on the beaches at [[Beeston Regis#Beeston Hill (Beeston Bump)|Beeston Bump]] and [[West Runton]].<ref>{{Cite web|url=http://www.museums.norfolk.gov.uk/default.asp?Document=400.500.100.030x2|archiveurl=https://web.archive.org/web/20071012025938/http://www.museums.norfolk.gov.uk/default.asp?Document=400.500.100.030x2|url-status=dead|title=Museums.norfolk.gov.uk|archivedate=12 October 2007}}</ref>

The "Ohio flint" is the official gemstone of Ohio state. It is formed from limey debris that was deposited at the bottom of inland [[Paleozoic]] seas hundreds of millions of years ago that hardened into [[limestone]] and later became infused with [[silica]]. The flint from Flint Ridge is found in many hues, including red, green, pink, blue, white, and grey, with the colour variations caused by minute impurities of [[iron compounds]].<ref>{{cite book |last1=McPherson |first1=Alan |title=State Geosymbols: Geological Symbols of the 50 United States |year=2011 |publisher=AuthorHouse |isbn=9781463442644 |url=https://books.google.com/books?id=T1Q8fpGYzPMC&pg=PA113 |access-date=28 March 2019 |archive-date=1 August 2020 |archive-url=https://web.archive.org/web/20200801190038/https://books.google.com/books?id=T1Q8fpGYzPMC&pg=PA113 |url-status=live }}</ref>

Flint can be sandy brown, medium to dark grey, black, reddish brown or an off-white grey in colour.<ref>http://prospectingnb.blogspot.com/2010_06_01_archive.html{{Dead link|date=January 2022 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

==Uses==

===Tools or cutting edges===
[[File:Feuersteinaxt.jpg|thumb|[[Neolithic]] flint axe, about 31 cm long]]
[[File:Folsom point.png|thumb|A 12,000 year old [[Folsom tradition]] spearpoint about {{cvt|3|inch|mm|order=flip}} long]]
Flint was used in the manufacture of tools during the [[Stone Age]], as it splits into thin, sharp splinters called flakes or blades (depending on the shape) when struck by another hard object (such as a [[hammerstone]] made of another material). This process is referred to as [[knapping]].<ref>{{cite book |last= Butler|first= Chris|date= 2005|title= Prehistoric Flintwork|publisher= The History Press|isbn= 9780752433400}}</ref>

[[Flint mining]] is attested since the [[Paleolithic]], but became more common since the [[Neolithic]] (notably among the [[Michelsberg culture]] and [[Funnelbeaker culture]]). In Europe, some of the best toolmaking flint has come from Belgium ([[Obourg]], flint mines of [[Spiennes]]),<ref>{{Cite web |url=http://www.minesdespiennes.org/en.html |title=Neolithic Flint Mines of Petit-Spiennes ''Official web site'' |access-date=16 December 2007 |archive-url=https://web.archive.org/web/20071231104655/http://minesdespiennes.org/en.html |archive-date=31 December 2007 |url-status=dead |df=dmy-all }}</ref> the coastal chalks of the [[English Channel]], the [[Paris Basin]], [[Thy (district)|Thy]] in [[Jutland]] (flint mine at [[Hou (Odder Municipality)|Hov]]), the Sennonian deposits of [[Rügen]], [[Grimes Graves]] in England, the Upper Cretaceous chalk formation of [[Dobruja]] and the lower [[Danube]] (Balkan flint), the Cenomanian chalky marl formation of the [[Moldavian Plateau]] (Miorcani flint), and the [[Jurassic]] deposits of the [[Kraków]] area and [[Krzemionki]] in Poland, as well as of the [[Lägern]] ([[silex]]) in the [[Jura Mountains]] of Switzerland.

In 1938, a project of the [[Ohio Historical Society]], under the leadership of H. Holmes Ellis began to study the knapping methods and techniques of [[Indigenous peoples of the Americas|Native Americans]]. Like past studies, this work involved experimenting with actual knapping techniques by creation of stone tools through the use of techniques like direct freehand percussion, freehand pressure and pressure using a rest. Other scholars who have conducted similar experiments and studies include [[William Henry Holmes]], [[Alonzo W. Pond]], [[Sir Francis Knowles, 5th Baronet|Francis H. S. Knowles]] and [[Don Crabtree]].<ref>Flenniken, J. Jeffrey. "The Past, Present, and Future of Flintknapping: An Anthropological Perspective." Annual Review of Anthropology 13 (1984): 187-203. http://www.jstor.org/stable/2155667 {{Webarchive|url=https://web.archive.org/web/20200910110255/https://www.jstor.org/stable/2155667 |date=10 September 2020 }}</ref>

To reduce susceptibility to fragmentation, flint/[[chert]] may be heat-treated, being slowly brought up to a temperature of {{convert|150|to|260|C|F|sigfig=2}} for 24 hours, then slowly cooled to [[room temperature]]. This makes the material more homogeneous and thus more [[wikt:knap|knappable]] and produces tools with a cleaner, sharper cutting edge. Heat treating was known to Stone Age artisans.{{citation needed|date=July 2019}}

===To ignite fire or gunpowder===
[[File:Flint spark lighter striking.jpg|thumb|A ferrocerium "flint" spark lighter in action{{Relevance inline|discuss=Ferrocerium lighter|date=August 2025}}]]

When struck against steel, a flint edge produces sparks. The hard flint edge shaves off a [[particle]] of the steel that exposes iron, which reacts with [[oxygen]] from the atmosphere and can ignite the proper [[tinder]].<ref name="angelfire">{{cite web |url=https://www.angelfire.com/journal2/firefromsteel/ |title=Fire from Steel – Custom forged fire steels from Roman through Fur Trade time periods |publisher=Angelfire.com |access-date=2013-07-21 |archive-date=25 January 2021 |archive-url=https://web.archive.org/web/20210125225311/https://www.angelfire.com/journal2/firefromsteel/ |url-status=live }}</ref> 

Prior to the wide availability of steel, rocks of [[pyrite]] (FeS<sub>2</sub>) would be used along with the flint, in a similar (but more time-consuming) way. These methods remain popular in [[woodcraft]], [[bushcraft]], and amongst people practising traditional fire-starting skills.<ref name=Bush>{{cite web|last1=Bush|first1=Darren|work=Manly Skills, Self-Reliance, Survival|title=Traditional Firestarting Part I: How to Make Fire with Flint and Steel|date=6 January 2011|url=http://www.artofmanliness.com/2011/01/05/traditional-firestarting-part-i-how-to-make-fire-with-flint-and-steel/|publisher=Art of Manliness|access-date=27 July 2015|archive-date=9 August 2020|archive-url=https://web.archive.org/web/20200809060116/https://www.artofmanliness.com/articles/traditional-firestarting-part-i-how-to-make-fire-with-flint-and-steel/|url-status=live}}</ref><ref name="Survival Cache">{{cite web|title=Do you have 5 Ways to Make Fire?|url=http://survivalcache.com/survival-fire-starters/|website=Survival Cache|access-date=27 July 2015|archive-date=12 February 2021|archive-url=https://web.archive.org/web/20210212001339/https://survivalcache.com/survival-fire-starters/|url-status=live}}</ref>

====Flintlocks====
[[File:Firesteels assorted.jpg|thumb|upright|left|Assorted reproduction [[firesteel]]s typical of [[Roman Empire|Roman]] to [[Medieval]] period]]

A later, major use of flint and steel was in the [[flintlock mechanism]], used primarily in [[flintlock]] firearms, but also used on dedicated fire-starting tools. A piece of flint held in the jaws of a spring-loaded hammer, when released by a trigger, strikes a [[hinged]] piece of steel ("[[frizzen]]") at an angle, creating a shower of sparks and exposing a charge of priming powder. The sparks ignite the priming powder and that flame, in turn, ignites the main charge, propelling the ball, bullet, or shot through the barrel. While the military use of the flintlock declined after the adoption of the [[percussion cap]] from the 1840s onward, flintlock rifles and shotguns remain in use amongst recreational shooters.

====Comparison with ferrocerium====

Flint and steel used to strike sparks were superseded in the 20th century by [[ferrocerium]] (sometimes referred to as "flint", although not true flint, "[[mischmetal]]", "hot spark", "metal match", or "fire steel"). This human-made material, when scraped with any hard, sharp edge, produces sparks that are much hotter than obtained with natural flint and steel, allowing use of a wider range of tinders. Because it can produce sparks when wet and can start fires when used correctly, ferrocerium is commonly included in [[survival kit]]s. Ferrocerium is used in many [[lighters]], where it is referred to as "a flint".

====Fragmentation====

Flint's utility as a fire starter is hampered by its property of uneven expansion under heating, causing it to fracture, sometimes violently, during heating. This tendency is enhanced by the impurities found in most samples of flint that may expand to a greater or lesser degree than the surrounding stone, and is similar to the tendency of [[Thermal fracturing in glass|glass to shatter]] when exposed to heat, and can become a drawback when flint is used as a [[building material]].<ref>{{cite web |url=http://web.ukonline.co.uk/scoutnotebook/fires/cooking.html |title=Building a cooking fire |archive-url=https://web.archive.org/web/20090525115954/http://web.ukonline.co.uk/scoutnotebook/fires/cooking.html |archive-date=May 25, 2009 |work=Scout Notebook |access-date=January 30, 2018 |year=2001}}</ref>

===As a building material===

Flint, knapped or unknapped, has been used from antiquity (for example at the Late Roman fort of [[Burgh Castle Roman Site|Burgh Castle]] in Norfolk) up to the present day as a material for building stone walls, using [[lime mortar]], and often combined with other available stone or [[brick]] rubble. It was most common in the parts of southern England where no good building stone was available locally, and where brick-making was not widespread until the [[late Middle Ages]]. It is especially associated with [[East Anglia]], but also used in chalky areas stretching through [[Hampshire]], Sussex, [[Surrey]] and [[Kent]] to [[Somerset]].

Flint was used in the construction of many churches, houses, and other buildings, for example, the large stronghold of [[Framlingham Castle]]. Many different decorative effects have been achieved by using different types of knapping or arrangement and combinations with stone ([[flushwork]]), especially in the 15th and early 16th centuries. Because knapping flints to a relatively flush surface and size is a highly skilled process with a high level of wastage, flint finishes typically indicate high status buildings.

During [[World War I]], in the chalky-soil country of France, the British filled [[sandbags]] with flint and used these sandbags as [[Breastwork (fortification)|breastworks]].<ref>Masefield, John, "The Old Frontline," The Macmillan Company, New York, Copyright 1917, pages 34-35. </ref>

<gallery>
File:flint church in england arp.jpg|A flint church – the Parish Church of Saint Thomas, in [[Cricket Saint Thomas]], Somerset, England. The height of the very neatly knapped flints varies between {{convert|3|and|5|in|cm}}.
File:Gariannonum Burgh Castle south wall well preserved close up.jpg|Close-up of the wall of the Roman [[Saxon Shore|shore fort]] at [[Burgh Castle Roman Site|Burgh Castle]], Norfolk, showing alternating courses of flint and [[Roman brick|brick]]
File:Surroundings of Canterbury Cathedral 02.JPG|A typical medieval wall (with modern memorial) at [[Canterbury Cathedral]] – knapped and unknapped ("cobble") flints are mixed with pieces of brick and other stones.
File:2004 thetford 03.JPG|Ruins of [[Thetford]] Priory show flints and mortar through the whole depth of the wall
</gallery>

===Ceramics===
Flint pebbles are used as the media in ball mills to grind glazes and other raw materials for the [[ceramics]] industry.<ref>{{cite book |title=Thoroughly Modern Milling |first=J.D. |last=Sawyer |series=American Ceramic Society Bulletin |volume=Bulletin&nbsp;86, No.&nbsp;6. |year=2007}}</ref> The pebbles are hand-selected based on colour; those having a tint of red, indicating high iron content, are discarded. The remaining blue-grey stones have a low content of [[chromophoric]] oxides and so are less [[deleterious]] to the colour of the ceramic composition after [[Pottery firing|firing]].<ref>{{cite book |title=Ceramics: Physical and chemical fundamentals |first1=H. |last1=Salmang |first2=M. |last2=Francis |publisher=Butterworths |year=1961}}</ref>

[[File:The name of the company on the site is now James Kent Limited. The three calcining ovens - formerly used for preparing flint for the ceramic industry are often known as 'salt, pepper and vinegar' by local people.jpg|thumb|Bottle kilns traditionally used for [[calcination|calcining]] flint]]
Until recently [[calcination|calcined]] flint was also an important raw material in clay-based [[ceramic]] bodies produced in the UK.<ref>{{cite book |title=Notes on the Manufacture of Earthenware |first=E.A. |last=Sandeman |publisher=The Technical Press Ltd. |year=1921}}</ref><ref name=Sugden-2001-IC-2>{{cite magazine |title=Changes & developments of non-plastic raw materials |last=Sugden |first=A. |magazine=International Ceramics |number=2 |year=2001}}</ref> In [[pottery|clay bodies]], calcined flint attenuates the shrinkage whilst drying, and modifies the fired [[thermal expansion]].<ref name="auto">{{cite book |title=Whitewares: Production, testing, and quality control |first1=W. |last1=Ryan |first2=C. |last2=Radford |publisher=Pergamon Press |year=1987}}</ref> Flint can also be used in [[Ceramic glaze|glazes]] as a network former.<ref>'Ceramics Glaze Technology.' Taylor J.R. & Bull A.C. The Institute Of Ceramics & Pergamon Press. 1986.</ref > In preparation for use flint pebbles, frequently sourced from the coasts of South-East England or Western France, were [[calcination|calcined]] to around {{cvt|1000|°C|-2}}. This heating process both removed organic impurities and induced certain physical reactions, including converting some of the quartz to [[cristobalite]]. After calcination the flint pebbles were crushed and milled to a fine particle size.<ref name="auto"/><ref>{{cite magazine |title=Use of flint in ceramics |magazine=Industrial Ceramics |number=885 |year=1993}}</ref><ref>{{cite magazine |title=Silica |first=Oelef |last=Heckroodt |magazine=Ceramic Review |number=254 |date=March–April 2012 |page=64}}</ref><ref>{{cite report |title=Calcination of Flint |first1=M. |last1=Manackerman |first2=E. |last2=Davies |series=Research Paper |volume=191 Part&nbsp;2: Continuous process in a vertical-shaft kiln |publisher=British Ceramic Research Association |year=1952}}</ref> However, the use of flint has now been superseded by [[quartz]].<ref name=Sugden-2001-IC-2/> Because of the historical use of flint, the word "flint" is used by some potters (especially in the U.S.) to refer generically to siliceous raw materials used in ceramics that are not flint.<ref>{{cite book |title=Ceramic Glazes |edition=3rd |last=Parmelee |first=C.W. |publisher=The Maple Press Company |year=1973}}<br/>{{cite book |title=Dictionary of Ceramics |edition=3rd |first=A. |last=Dodd |publisher=The Institute of Materials |year=1994}}<br/>{{cite book |title=The Potter's Dictionary of Materials and Techniques |first1=F. |last1=Hamer |first2=J. |last2=Hamer |place=London, UK |publisher=A. & C. Black |year=2004}}</ref><ref>{{cite conference |first=C.M. |last=Marsh |year=1978 |title=Flint and silica |book-title=Proceedings of the American Ceramic Society Annual Meeting 1978; Materials, Equipment, & Whitewares Division}}</ref><ref>{{cite magazine |title=Stoneware clay body formulas. Part&nbsp;2: The perfect body |first=J. |last=Zamek |magazine=Ceramics Industry |volume=155 |number=10 |year=2005}}</ref>

===Jewelry===
{{See also|Ancient Egyptian flint jewelry}}
Flint bracelets were known in [[Ancient Egypt]], and several examples have been found.<ref>{{cite web|last=Graves-Brown|first=Carolyn|title=AB29 Flint bracelet|url=http://www.egypt.swansea.ac.uk/index.php/collection/297-ab29.htm|publisher=Swansea University|access-date=13 January 2011|url-status=dead|archive-url=https://web.archive.org/web/20121029080451/http://www.egypt.swansea.ac.uk/index.php/collection/297-ab29.htm|archive-date=29 October 2012|df=dmy-all}}</ref>

==See also==

'''Mineralogy'''
* {{annotated link|Agate}}
* {{annotated link|Chalcedony}}
* {{annotated link|Eolith}}
* {{annotated link|Jasper}}
* {{annotated link|Nodule (geology)}} not to be confused with [[concretion]]
* {{annotated link|Obsidian}}
* {{annotated link|Onyx}}
* {{annotated link|Opal}}
* {{annotated link|Whinstone}}
'''Archaeology'''
* {{annotated link|Clovis Point|Clovis points}}, archaeological artefacts of the [[Clovis culture]] in [[New Mexico]], US
* {{annotated link|Grimes Graves}}, a prehistoric flint mine in [[Norfolk]], England
* {{annotated link|Flint Ridge State Memorial}}, a Native American flint quarry in [[Hopewell Township, Licking County, Ohio|Hopewell Township]], Licking County, Ohio, US
* {{annotated link|Flint mine}}

==References==
{{reflist|25em}}

==External links==
{{Sister project links|auto=y|wikt=y}}
* [http://www.gilesdelamare.co.uk/page3.htm Flint Architecture of East Anglia] Book by Stephen Hart
* [http://www.flintsource.net/ Flintsource.net European Artefacts – detailed site]
* [http://www.geulogy.com/introdis-beestonbump.html Flint circles and paramoudra – Beeston Bump] {{Webarchive|url=https://web.archive.org/web/20171228172125/http://www.geulogy.com/introdis-beestonbump.html |date=28 December 2017 }}
* [https://web.archive.org/web/20090602145732/http://www.electricyouniverse.com/eye/index.php?level=album&id=71 Paramoudras and flint circles photograph collection]
* [https://web.archive.org/web/20110928094719/http://www.kimwilkie.com/pages/projects/uk/uk_wcath.html Winchester Cathedral Close]
* [https://www.buildingconservation.com/articles/flint/flint.htm Flint and the Conservation of Flint Buildings] Introduction to the historical use of flint in construction and the repair and conservation of historic flint buildings

{{Silica minerals}}
{{Firelighting}}
{{Rock type}}
{{Authority control}}

[[Category:Flint (rock)| ]]
[[Category:Sedimentary rocks]]
[[Category:Chert]]
[[Category:Lithics]]
[[Category:Fire making]]
[[Category:Building stone]]