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Sedimentary rock
Miorcani flint.jpg
A sample of Miorcani flint from the Cenomanian chalky marl layer of the Moldavian Plateau (c.7.5 cm (3.0 in) wide)
Cryptocrystalline quartz
A piece of flint 9-10 cm (3.5-3.9 in) long, weighing 171 grams Flint, 9cm, 171gm.jpg
A piece of flint 9–10 cm (3.5–3.9 in) long, weighing 171 grams

Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, [1] [2] categorized as the variety of chert that occurs in chalk or marly limestone. Flint was widely used historically to make stone tools and start fires.


Flint occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones. [3] [4] 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 streams and beaches.

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 flint. Flint Ridge in Ohio was an important source of flint, and 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. [5]

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 Although it has been superseded in these uses by different processes (the percussion cap), or materials (ferrocerium), "flint" has lent its name as generic term for a fire starter.


Silicified remains of algae and silica pseudomorph after halite in flint. Pebble of Loire near Marcigny, France. Image width: about 5 mm. Silica pseudomorph after halite crystals and silicified remains of algae 6.jpg
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 silicified. This hypothesis would certainly 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 (demosponges). [3] Certain types of flint, such as that from the south coast of England and its counterpart on the French side of the Channel, contain trapped fossilised marine flora. Pieces of coral and vegetation have been found preserved inside the flint similar to insects and plant parts within amber. Thin slices of the stone often reveal this effect.

Pebble beach made up of flint nodules eroded from the nearby chalk cliffs, Cape Arkona, Rugen, northeast Germany. Flintbeach.jpg
Pebble beach made up of flint nodules eroded from the nearby chalk cliffs, Cape Arkona, Rügen, northeast Germany.

Flint sometimes occurs in large flint fields 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 Bump and West Runton. [6]

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 like red, green, pink, blue, white and grey, with the colour variations caused by minute impurities of iron compounds. [7]

Flint can be coloured: sandy brown, medium to dark grey, black, reddish brown or an off-white grey. [8]


Tools or cutting edges

Neolithic flint axe, about 31 cm long Feuersteinaxt.jpg
Neolithic flint axe, about 31 cm long
A 12,000 year old Folsom tradition spearpoint about 76 mm (3 in) long Folsom point.png
A 12,000 year old Folsom tradition spearpoint about 76 mm (3 in) 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. [9]

Flint mining is attested since the Paleolithic, but became more common since the Neolithic (Michelsberg culture, Funnelbeaker culture). In Europe, some of the best toolmaking flint has come from Belgium (Obourg, flint mines of Spiennes), [10] the coastal chalks of the English Channel, the Paris Basin, Thy in Jutland (flint mine at 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 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, Francis H. S. Knowles and Don Crabtree. [11]

To combat fragmentation, flint/chert may be heat-treated, being slowly brought up to a temperature of 150 to 260 °C (300 to 500 °F) for 24 hours, then slowly cooled to room temperature. This makes the material more homogeneous and thus more knappable and produces tools with a cleaner, sharper cutting edge. Heat treating was known to Stone Age artisans.[ citation needed ]

To ignite fire or gunpowder

A ferrocerium "flint" spark lighter in action Flint spark lighter striking.jpg
A ferrocerium “flint” spark lighter in action

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. [12]

Prior to the wide availability of steel, rocks of pyrite (FeS2) 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. [13] [14]


Assorted reproduction firesteels typical of Roman to Medieval period Firesteels assorted.jpg
Assorted reproduction firesteels typical of 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 man-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 kits. Ferrocerium is used in many cigarette lighters, where it is referred to as "a flint".


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 glass to shatter when exposed to heat, and can become a drawback when flint is used as a building material. [15]

As a building material

Flint, knapped or unknapped, has been used from antiquity (for example at the Late Roman fort of 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 those parts of southern England where no good building stone was available locally, and where brick-making was not widespread until the later 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 breastworks. [16]


Flint pebbles are used as the media in ball mills to grind glazes and other raw materials for the ceramics industry. [17] 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 firing. [18]

Bottle kilns traditionally used for calcining flint 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
Bottle kilns traditionally used for calcining flint

Until recently calcined flint was also an important raw material in clay-based ceramic bodies produced in the UK. [19] [20] In clay bodies calcined flint attenuates the shrinkage whilst drying, and modifies the fired thermal expansion. [21] Can also be used in glazes as a network former. [22] In preparation for use flint pebbles, frequently sourced from the coasts of South-East England or Western France, were calcined to around 1,000 °C (1,800 °F). 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. [23] [24] [25] [26] However, the use of flint has now been superseded by quartz. [20] 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. [27] [28] [29]


Flint bracelets were known in Ancient Egypt, and several examples have been found. [30]

See also



Related Research Articles

<span class="mw-page-title-main">Ceramic</span> Inorganic, nonmetallic solid prepared by the action of heat

A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain, and brick.

<span class="mw-page-title-main">Chalcedony</span> Microcrystalline varieties of silica, may contain moganite as well

Chalcedony ( kal-SED-ə-nee, or KAL-sə-doh-nee) is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic. Chalcedony's standard chemical structure (based on the chemical structure of quartz) is SiO2 (silicon dioxide).

<span class="mw-page-title-main">Chert</span> Hard, fine-grained sedimentary rock composed of cryptocrystalline silica

Chert is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood.

In archaeology, a tool stone is a type of stone that is used to manufacture stone tools, or stones used as the raw material for tools.

A stone tool is, in the most general sense, any tool made either partially or entirely out of stone. Although stone tool-dependent societies and cultures still exist today, most stone tools are associated with prehistoric cultures that have become extinct. Archaeologists often study such prehistoric societies, and refer to the study of stone tools as lithic analysis. Ethnoarchaeology has been a valuable research field in order to further the understanding and cultural implications of stone tool use and manufacture.

<span class="mw-page-title-main">Knapping</span> Shaping of conchoidal fracturing stone to manufacture stone tools

Knapping is the shaping of flint, chert, obsidian, or other conchoidal fracturing stone through the process of lithic reduction to manufacture stone tools, strikers for flintlock firearms, or to produce flat-faced stones for building or facing walls, and flushwork decoration. The original Germanic term knopp meant to strike, shape, or work, so it could theoretically have referred equally well to making statues or dice. Modern usage is more specific, referring almost exclusively to the hand-tool pressure-flaking process pictured. It is distinguished from the more general verb "chip" and is different from "carve", and "cleave".

In archaeology, lithic analysis is the analysis of stone tools and other chipped stone artifacts using basic scientific techniques. At its most basic level, lithic analyses involve an analysis of the artifact's Morphology (archaeology), the measurement of various physical attributes, and examining other visible features.

<span class="mw-page-title-main">Conchoidal fracture</span> Brittle fracture surface that does not follow any natural planes of separation

Conchoidal fracture describes the way that brittle materials break or fracture when they do not follow any natural planes of separation. Mindat.org defines conchoidal fracture as follows: "a fracture with smooth, curved surfaces, typically slightly concave, showing concentric undulations resembling the lines of growth of a shell". Materials that break in this way include quartz, chert, flint, quartzite, jasper, and other fine-grained or amorphous materials with a composition of pure silica, such as obsidian and window glass, as well as a few metals, such as solid gallium.

<span class="mw-page-title-main">Stoneware</span> Term for pottery or other ceramics fired at a relatively high temperature

Stoneware is a rather broad term for pottery fired at a relatively high temperature. A modern definition is a vitreous or semi-vitreous ceramic made primarily from stoneware clay or non-refractory fire clay. End applications include tableware, decorative ware such as vases.

<span class="mw-page-title-main">Silicosis</span> Pneumoconiosis caused by inhalation of silica, quartz or slate particles

Silicosis is a form of occupational lung disease caused by inhalation of crystalline silica dust. It is marked by inflammation and scarring in the form of nodular lesions in the upper lobes of the lungs. It is a type of pneumoconiosis. Silicosis is characterized by shortness of breath, cough, fever, and cyanosis. It may often be misdiagnosed as pulmonary edema, pneumonia, or tuberculosis. Using workplace controls, silicosis is almost always a preventable disease.

<span class="mw-page-title-main">Fire clay</span> Refractory clays used in ceramics manufacturing

Fire clay is a range of refractory clays used in the manufacture of ceramics, especially fire brick. The United States Environmental Protection Agency defines fire clay very generally as a "mineral aggregate composed of hydrous silicates of aluminium (Al2O3·2SiO2·2H2O) with or without free silica."

<span class="mw-page-title-main">Chrysoprase</span> Apple-green, gem-quality, chalcedony variety

Chrysoprase, chrysophrase or chrysoprasus is a gemstone variety of chalcedony that contains small quantities of nickel. Its color is normally apple-green, but varies to deep green. The darker varieties of chrysoprase are also referred to as prase.

<span class="mw-page-title-main">Novaculite</span>

Novaculite, also called Arkansas Stone, is a microcrystalline to cryptocrystalline rock type that consists of silica in the form of chert or flint. It is commonly white to grey or black in color, with a specific gravity that ranges from 2.2 to 2.5. It is used in the production of sharpening stones. It occurs in parts of Arkansas, Oklahoma, and Texas, as well as in Japan and parts of the Middle East. The name novaculite is derived from the Latin word novacula, meaning a sharp knife, dagger, or razor, in reference to its use in sharpening. The first recorded use of the term whetstone was in reference to a honing stone from Arkansas.

<span class="mw-page-title-main">Fire striker</span> Carbon steel for making sparks

A fire striker is a piece of carbon steel from which sparks are struck by the sharp edge of flint, chert or similar rock. It is a specific tool used in fire making.

<span class="mw-page-title-main">Nodule (geology)</span> Small mass of a mineral with a contrasting composition to the enclosing sediment or rock

In sedimentology and geology, a nodule is a small, irregularly rounded knot, mass, or lump of a mineral or mineral aggregate that typically has a contrasting composition, such as a pyrite nodule in coal, a chert nodule in limestone, or a phosphorite nodule in marine shale, from the enclosing sediment or sedimentary rock. Normally, a nodule has a warty or knobby surface and exists as a discrete mass within the host strata. In general, they lack any internal structure except for the preserved remnants of original bedding or fossils. Nodules are closely related to concretions and sometimes these terms are used interchangeably. Minerals that typically form nodules include calcite, chert, apatite (phosphorite), anhydrite, and pyrite.

This is a list of pottery and ceramic terms.

<span class="mw-page-title-main">Mill Creek chert</span>

Mill Creek chert is a type of chert found in Southern Illinois and heavily exploited by members of the Mississippian culture. Artifacts made from this material are found in archaeological sites throughout the American Midwest and Southeast. It is named for a village and stream near the quarries, Mill Creek, Illinois and Mill Creek, a tributary of the Cache River. The chert was used extensively for the production of utilitarian tools such as hoes and spades, and for polished ceremonial objects such as bifaces, spatulate celts and maces.

<span class="mw-page-title-main">Glossary of firelighting</span>

This is an alphabetized glossary of terms pertaining to lighting fires, along with their definitions. Firelighting is the process of starting a fire artificially. Fire was an essential tool in early human cultural development. The ignition of any fire, whether natural or artificial, requires completing the fire triangle, usually by initiating the combustion of a suitably flammable material.

<span class="mw-page-title-main">Upper Mercer flint</span>

Upper Mercer flint or Upper Mercer chert is a type of flint, or a pure form of chert, found in Coshocton, Hocking, and Perry counties of Ohio. Made of forms of silica and quartz, the hard and brittle stone was used by prehistoric people to make tools and weapons. To create stone tools, flint was heated to make chipping away at the stone easier, and then the flint was chipped to form razor-sharp edges. Resulting tools included spearheads, scrapers, knives, and arrows.


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