Definitions

flint heads

Flint

[flint]

Flint (or flintstone) is a hard, sedimentary cryptocrystalline form of the mineral quartz, categorized as a variety of chert. It occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones. Inside the nodule, flint is usually dark grey, black, green, white, or brown in colour, and often has a glassy or waxy appearance. A thin layer on the outside of the nodules is usually different in colour, typically white, and rough in texture. From a petrological point of view, "flint" refers specifically to the form of chert which occurs in chalk or marly limestone. Similarly, "common chert" (sometimes referred to simply as "chert") occurs in limestone.

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 theory certainly explains the complex shapes of flint nodules that are found. The source of dissolved silica in the porous media could arise from the spicules of silicious sponges.

Uses

Tools

Flint was used for the manufacture of flint 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.

In Europe, some of the best toolmaking flint has come from Belgium (Obourg, flint mines of Spiennes), 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 and the Jurassic deposits of the Kraków area in Poland. Flint mining is attested since the Palaeolithic, but became more common since the Neolithic (Michelsberg culture, Funnelbeaker culture).

Fire

When struck against steel, flint will produce sparks, which when directed onto tinder can be used to start a fire. This occurs when the hard flint knocks off a particle of the steel, which is heated by the impact, and then burns with oxygen from the atmosphere. This method is popular in woodcraft and among campers who want to have an 'authentic' experience. The components are also part of many survival kits, such as those issued by many military units, because they have the ability to work while wet, have a very long shelf-life, and will last a very long time in an extended survival situation (unlike matches or a lighter which not only need to be specially design to be able to light when wet, but which would be exhausted sooner than a flint-and-steel fire starter in a longer-duration survival scenario). Striking a lump of flint against a piece of steel to make fire is not particularly easy or convenient (although it is much easier than other primitive fire-making methods such as using a bow and drill, and requires little practice to employ). Matches and lighters are a much quicker and more convenient way of starting a fire, but have the disadvantages of being unable to function when wet (except for special designs) and of being more limited (than flint and steel) in the number of times that they can be used before exhausting their fuel supply.

Even so, many lighters still use a variant of the ancient technology as the ignition source for their primary fuel, due to the ease with which those materials generate a sufficiently hot spark. Ferrocerium now replaces the steel and has been miniaturized and integrated into such lighters. The ferrocerium used in these lighters, while sometimes called "flint", has the opposite role than the flint in true flint-and-steel. Ferrocerium is much softer than modern steel and can be scraped with knife with minimal damage to the knife. In lighters, a small steel wheel is turned by the user rotating it with the thumb, creating a high-temperature spark, which ignites the lighters' primary fuel source (which is either present, such as in liquid fuel lighters, or which is also released by the same thumb motion, such as in butane-gas lighters), which then produces a small flame that burns until extinguished. Common examples include the disposable Bic lighter and the reusable Zippo lighter. The small ferrocerium cylinder in Zippo's spark producing mechanism is eventually consumed, and Zippo and other companies (e.g., Ronson) sell replacements that are marketed as "flints," even though they are ferrocerium. Such mechanisms are more popular in liquid fuel lighters than in butane-gas lighters, which more commonly have a piezoelectric ignition system.

A later major use was to create the spark that would ignite the powder that would fire a ball or bullet from a flintlock firearm. While the military use of a flintlock declined after the British military generally applied the percussion cap on their muskets in 1842, it is still popular to use the flintlock as a hunting rifle during special muzzleloader seasons or general rifle seasons in several states in the US.

Building

Flint, knapped or unknapped, has been used since 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 parts of southern England, where no good building stone was available locally, and brick-making not widespread until the later Middle Ages. It is especially associated with East Anglia, but also used in chalky areas stretching through 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.

Ceramics

Flint pebbles are used as the media in ball mills to grind glazes and other raw materials for the ceramics industry. The pebbles are hand-selected for colour, with those showing a reddish tint, indicating the presence of iron, being discarded. The remaining blue-grey stones have a low content of chromophoric oxides and so should impart lesser amounts of colouring contaminants.

In the UK, flint pebbles were traditionally an important raw material for clay-based ceramic bodies. After calcination to remove organic impurities and induce certain physical reactions, and milling to fine particle size, flint was added as a filler to pottery bodies. However, flint is no longer used and has been replaced by quartz as is used in other countries. Because of this historical use, the word "flint" is used by US potters to refer to siliceous materials which are not flint.

See also

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