Flint

Voor de Nederlandse versie van het artikel klik hier

Anyone who has ever walked on the beach, especially in southern England, has found flint. For most people not really a special, attractive or beautiful stone. Ok, sometimes they have interesting shapes or beautiful colours. But how ordinary this stone might be, no rock or mineral has had so much influence on human history as flint. This makes it one of the most important, if not the most important rock in human history.

Geology
Flint is a cryptocrystalline quartz rock, chemical formula SiO2. It can have many colours, ranging from black to grey and from red to brown. These colours are caused by contamination with i.e. chalk and iron or organic material. The way flint is created is subject of debate. In England (actually across the whole of Europe) you find flint almost always as concretions or as layers in chalk or limestone. (Want the read more about chalk and the white cliffs? Click here). Sometimes in narrow bands, sometimes in thicker layers. If you’ve walked on the beach at the white cliffs, you’ve probably seen that the white chalk contains dark layers that are made of flint.

100_6371
Dark bands of flint in the white chalk at the Seven Sisters

Flint is always a marine deposit, a seawater deposit. Silicon dioxide, the building blocks of quartz, dissolve in waterv at high temperature (no worries, your quartz crystal really does not dissolve in boiling water at once). Each SiO2 molecule binds with two water molecules (H2O). Those togehter form silicic acid, SiO2 2H2O. Some readers now think, hey, that’s the chemical formula of Opal! True, opal is in fact quartz with water. It depends on the type of opal which part of the stone actually consists of water molecules (no physical, touchable water as with enhydro agate). Actually, Opal is silicified and petrified silicic acid that crystallized so fast that it didn’t have time to form a crystal lattice (it is amorphous, without a crystal system) and that has not been exposed to such pressure or conditions that the water has disappeared. Opal is not officially a mineral, but a mineraloid. But it has the same chemical base as quartz and partly forms the same way as flint. And it was flint we talked about, so back to the white cliffs. Seawater normally contains little silica. Silica-containing water is often seen after volcanic eruptions in the cavities in the solidified lava. That is why quartz geodes form in here. But in seawater it has to come from somewhere else. The theory is that the silica from which flint is formed comes from animal remains. Microscopically small skeletal particles of micro-organisms in the sea. Some scientists think that diatoms and radiolaria are the main source, others believe that sponges are. Of all these animals fossils have been found in flint. In addition to the organic origin, silica-containing water also enters the sea through groundwater in which silica is dissolved from the soil and through clay particles that wash into the sea and dissolve in sea water. Flint is very fossiliferous anyway and the fossils are often very well preserved in flint. For example sea urchins, shells, ammonites, etc.

667D8083-8D0E-4CB7-B2C2-BED558694B1E
Flint echinoid, seu urchin, from the Cliffs near Broadstairs (Kent)

Flint is created on the seabed. In addition to the silica that is already in the water, the bottom layer of seawater receives additional silica as a result of the death and descent of the aforementioned animals with a silica skeleton (diatoms, radiolaria and sponges already living on the bottom) ). Due to this high silica content in this layer, it turns into a siliceous ooze and then into quartz (chalcedony) which forms when the saturation limit is reached. Depending on the circumstances, saturation, temperature, etc., a gel-like substance, this so called siliceous ooze, forms that will petrify. At first this still contains a lot of water and is therefore technically a type of opal. Ordinary opal, not super the nice and pretty coloured Australian gem quality, is also known as opalite, not to be confused with the coloured man-made glass that is sometimes sold under the same name. As the percentage of water decreases, the rock becomes harder and gets more petrified. Until finally all the water has disappeared and it is actually a type of quartz, flint in this case. Now that you know how this happens, you also understand why flint has been deposited in cavities in the seabed, because this silica water settles in it and tunrs into rock. This is also the reason why you sometimes find tiny sparkling crystals or botryoidal chalcedony in flint nodules. These are quartz crystals and are made of the same elements as flint.

05E1A3E6-7A1E-4BAF-AD08-F560EAE0C08A
Botryoidal chalcedony in flint, Seaton

Many of these cavities are made by animals that live in the seabed, such as crustaceans. These critters dig a way through the seabed and in the burrows flint eventually forms. Hence flint concretions can have the most amazing shapes. These petrified burrows are not fossils, after all they are not actual imprints or physical remains from the animal. We call these types of remains ichnofossils, trace fossils. Just like, for example, saurian footsteps or crawling traces of trilobites are ichnofossils. The ‘skin’ of a flint concretion is often white, this is chalk. This layer is called the cortex. Sometimes flint can also have beautiful bands. This is the so-called banded flint. In southern England, the colour of the rock sometimes tells where the flint comes from. In the Southeast, the white cliffs area, the flint is comes in a range from pale gray to black. Further west, towards Dorset, the flint becomes more reddish brown in colour. In the Netherlands we find a lot dark black flint in Zeeland. A very beautiful deep red flint comes from Helgoland. The erratic flint in the Netherlands has all kinds of colours. Most common are gray and orange-brown.

The Dutch word for flint is vuursteen, fire stone. So is the German word, Feuerstein. The English word flint is based on the way the rock splits when you hammer it. Why is flint actually called a firestone? Because you can make fire with it of course. Hit a piece with another piece of flint and you see small sparks of fire. But together with a piece of pyrite, marcasite or metal a flint gives even larger sparks that can ignite dry, flammable material. The names associated with flint are somewhat confusing anyway. Flint belongs to the cryptocrystalline quartzes and is therefore a type of chalcedony. But it is not described as mineral, it is a rock. You often come across the name silex when you read about flint. This is the Latin and also French word for flint and is now also used as a synonym in Dutch and English. In building materials and paint, silex is also used as a name for flint or quartz powder. The name flint is only given to flint in chalk or limestone. But you also see the word chert being used for flint. Chert is in fact the English name for all silica-containing rocks, of which flint is a very pure form.

Flint is not tied to a geological period and has been formed ever since the pre-Cambrian period. But almost all flint found in Europe is deposited in the period that we call the Cretaceous. We have flint mines in Limburg, which are Upper Cretaceous, Maastrichtian. In northern France and southern England, in the famous chalk cliffs, lies an enormous amount of flint, varying in age from Cenomanian to Santonian. A lot of flint can also be found in Scandinavia and on the beaches in North Germany.The flint that you can find in the Netherlands is deposited here ‘in situ’ in Limburg during the Cretaceous, transported by rivers from the south or brought in by giant glaciers from the north during the penultimate ice age, the Saaliën or Saale / Riss ice age in Europe, Wolstonian Stage in the UK.

Flint, its use and meaning for us
When you smash or hammer flint, razor-sharp pieces with a very typical, shell-shaped fracture come off. For someone who has done this many times, a lot of practice makes it possibple to predict how and where this fracture will happen. The theory behind this has to do with the principle of the ‘Herzian cone’, the form in which a piece of cryptocrystalline quartz always chips when hit by a hard object (for example the cone shaped hole a bullet makes in a glass window). This in combination with the razor-sharp edges makes flint ideal for making all kinds of tools. And man has gratefully made use of it. The oldest finds of stones that would have been used as tools come from Africa and date from 3.3 million years ago, that is older than the oldest people. The first ‘real’ stone tools in Europe were so-called ‘chopping tools’. These were not necessarily made of flint and are often not immediately recognizable as tools for the untrained eye. The technique of stone working became more and more refined over time and when people discovered the distinct properties of flint they could make better tools. Moreover, flint was available almost everywhere. Modern archaeologists appoint pre-historic cultures to the way the stone was worked. The period in history in which stone tools were used has also adopted its name form these stone tools, the ‘Stone Age’, subdivided into paleolithic, mesolithic and neolithic. Early stone age, middle stone age and late stone age. The oldest European finds of the typical worked flint axes date from the Early Paleolithic, Acheulean culture, and have been found with remains of Homo erectus. This culture was probably originally developed by Homo habilis in Africa. Over time, many cultures have emerged their own method of stone working. Fossils in flint also played a role. Flint that contains a fossil that has sometimes been worked in such a way that the fossil had a prominent place in the tool. An example of this is a flint axe with a sea urchins from Homo heidelbergensis, 400,000 years old and a Neanderthal axe from Norfolk with a fossil shell, 200,000 years old. A recent study also shows that Neanderthals had an eye for the beauty of stone and that they kept exceptionally beautiful pieces of flint.

B6F916C0-890B-474D-A68E-C2D2B82BD132
Flint arrowhead

Cro-Magnon man refined the flint chopping technique so that they could hammer off very thin and sharp blades and make tiny arrowheads. Flint was so important to early people that it was mined. In Limburg near Rijckholt, in England, Grimes Graves is the remnant of intensive flint mining. The largest flint mines in Europe were in Belgium and France, including the ones near Spiennes. These are now on the World Heritage List of UNESCO. The origin of flint can often be traced by the microfossils, so many flint tools can be traced back to where they were made (or where the rough material came from). That is why we know that pieces of flint could ‘travel’ long distances with their owner(s).

Homo sapiens later developed even more refined techniques for working stone, including polishing. Many (ritual) war hammers have been found that are polished, but they are not always made of flint. Flint tools can be found on auction websites or at antique dealers, but unfortunately there is a lot of counterfeiting. Some people can make perfect, ancient looking, axes and arrows. Most use this skill for education, to give demonstrations to the public, but unfortunately some people atry to make money this way and sell counterfeits as archaeological finds. The presence of patina, wind varnish, on flint is an important characteristic of flints that have been on the ground, exposed to wind and weather for a long time. This creates a shiny polish on the stone, as if it has been polished by the elements. But this is not always a thrustworthy judgemental feature. Many archaeological pieces do not have this because they were buried and people nowadays find ways to imitate this patina. The science considering stone tools is very extensive and complex. What I write here is very concise, learning more about this is a study in itself.

The usefulness of flint after the Stone Age was primarily that of making fire. It was used as ingnition tool until after the Middle Ages. For example as small flint pieces in flintlock guns with gunpowder. But it was also very popular as a building material. Large quantities were available, easy to mine and extremely hard and weather-resistant. Complete castles are built from flint. But also many houses, farms, walls in the landscape, etc. In southern England you can find many churches and castles that are partly or entirely built of flint that came from local small quarries in the chalk. The castle of Lewes is a very good example of this.

Modern human after prehistoric times did not know what to think of flint arrows and axes found on ploughed fields. They called them thunderstones. They believed that they would protect against being hit by lightning and disaster. Vikings and Germanic people associated them with their thunder gods Thor and Donar. Scandinavians poured beer over these axes as a sacrifice to the gods. Children wore them as an amulet to protect them against evil magic. The Romans hung arrowheads on a dog’s collar to protect the dog against rabies. In Sweden flint arrows would protect against mischief of the fairies. In Great Britain the arrowheads were also called fairy arrows because they believed that the fairies shot arrows at people to enchant them.

Urns with cremation remains and flint arrowheads from Roman timeshave been found in Great Britain. Probably because fire-producing stones were seen as extgremely magical and they had to prevent the deceased from rising from the dead. In Ireland, arrowheads were put in water to give healing powers to the water and they wore arrowheads cast in silver to prevent diseases and troubles caused by the fairies. In the Middle Ages people believed flint axes had fallen on earth during the ‘heavenly war’ against the devil. That is why flint axes were considered very sacred and were regarded as a valuable gifts by bishops and kings. From the 18th century on people realized that these stones were actually tools made by prehistoric people.

In esotheric and New Age shops you see more and more flint for sale that, because it comes from a certain place, is said to have extra healing powers. For example, flint from a crop circle or from a sacred place like burial mounds or stone circles. I want to make two remarks about this. Nobody can see if the stone really comes from that place, it is very easy to believe, but be careful. You might pay a whole lot of money for a piece of flint from your local beach. Secondly, what damage is done to a historically and archaeologically important place when all flint is taken away to be sold….
These might pieces that can teach us more about the people who made this stone circle, tomb, etc. Gone for archaeological research and gone from the site where it actually belongs and where it was perhaps laid with a certain intention by people who buried a leader or loved one there. Only for a fancy name and therefore more money in a shop.

 

 

 

 

 

 

 

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s