Identifying flint tools
Identifying flint tools and weapons is more of an art than a
science and experience is ultimately the best guide. However,
there is a list of important indications of human manufacture and
the more of them you can find in a flint, the more probable it is
that you have found a stone age tool.
To understand the significance of much of the following list of
criteria, you need to appreciate first how flint tools are made (click
An identification checklist
To distinguish between an artefact and a geofact (a flint that
has been shaped by natural processes such as frost) use the
following checklist. Don't pay too much attention to the overall
shape or possible function (whether it would make a good borer or
spear point) but ask yourself:
- Is the flint uniformly patinated?
- Is there the remains of a striking platform?
- Is there a striking point (positive bulb of percussion)?
- Have the edges been retouched?
If the flint is uniformly patinated over all its facets
(or all the facets on one side) then it is possible it could be of
human make. If different facets have different degrees of
patination, this is an indication they were not made at the same
time, so the flint is less likely to be an artefact. (See
pictures at right and discussion
on patination below for further details of this complex subject).
Re-touching of one or more edges is a sure sign of human
manufacture. Unfortunately it can sometimes be confused with edge
damage that has been caused by knocking against the plough or
other stones in the field. This is one reason why uniform patination is
important, since random damage will have differential levels of
patination. Edge damage tends to be random and discontinuous,
while retouching is usually continuous and even overlapping. (See
examples of re-touching here).
Known design type
Stone age toolmakers tended to stick
to relatively few established design patterns such as the side scraper or end
scraper and hence these are the types most commonly found. If a
flint conforms closely to a well-known design, that is a useful
positive indication. (Learn more about tool
types here and see Tools
Galleries for examples)
Flint - the chameleon stone
Flint is a surprisingly complex material and much about its
formation and the way it weathers is still subject for debate. (See
here for more information). In the United States, flint
is often referred to generically as chert - a term that is usually
reserved in Britain for poor quality flint.
In essence, flint is a form of quartz that has a microscopically
structure and various other minerals included within that
structure. Different mineral inclusions give rise to
different colorations. The following are all forms of flint:
Agate, Carnelian, Chalcedony, Jasper, Obsidian, Onyx and Opal.
Flint is close behind diamond as one of the hardest minerals. Because of its
microscopically small crystalline structure and its inclusion of
other minerals, flint is able to take an edge only a few molecules
thick without breaking - thinner than fine steel. Flint can
be - literally - sharper than a razor.
Much flint in Southern England, when freshly broken,
is often a dark, almost
black colour, or darkish grey, sometimes with lighter
inclusions. As it becomes patinated, the exterior skin tends to
assume a lighter colour, often with a milky, opalescent
sheen. Once a worked flint has become patinated all over,
the patina often becomes stained with the colour of the ground in which it
lays. If there are iron minerals dissolved in the ground
waters locally, the patina will be reddish brown.
flint lays in chalky ground, it is likely to become patinated
white. Sometimes, rust coloured spots appear on flints and are
specially noticeable on white patinated flints. The spots often
form on or near ridges between flake scars and are known as 'iron
Patination as a guide to age
The formation of a patina, or surface
coating on flints is a complex chemical process that is still not
fully understood. It can sometimes, though, give a useful rough
indication of the age of a worked flint, providing some important
exceptions are kept in mind.
In general, when a freshly broken flint surface is exposed to
surrounding soil and water, a patina begins to form. How fast this
process happens, depends on a large number of factors, some of
which are described in more detail below. They include the acidity
of the soil, the exact crystalline nature of the silica at the
flint surface and the mineral inclusions in the flint.
There are two distinct kinds of patina – porous and glossy -
and a worked flint can have one, both, or neither. The first is a
dull whitish external coat that closely resembles the cortex that
forms around flint nodules in the native chalk beds in which they
first formed in the Cretaceous period of the Earth’s history.
This original form is often many millimetres thick – presumably
because of the great length of time over which it formed.
The whitish cortex that forms on a humanly worked flint is
never of such great thickness (usually only a tiny fraction of a
millimetre thick). But its cause may well be similar. Water at the
surface of the flint can – over long periods – dissolve some
microscopically small regions quicker than others. The result
(seen through a microscope) is a surface layer with a structure like a
sponge or coral. This
refracts light in such a way as to appear white.
It’s very common to find worked (and natural) flints
patinated in this way in close contact with chalk rocks or chalky
soil. If there are any iron minerals in the surrounding soil, they
will tend to stain the sponge-like surface layer reddish brown.
There is also a second kind of patination that takes place over
time and is called gloss patination. (Note that this is not the
same as gloss caused by external abrasion such as desert
sandstorms or tumbling in a river, or human use). Gloss patination
is a natural chemical process. It results in both a shiny surface
gloss and the 'blunting' of sharp edges including retouching and
edges between flake removal scars.
In a 2002 study of the phenomenon, Calvin D Howard, concluded
that the most likely cause is the dissolving of silica from the
flint surface by ground water, which is then redeposited on the
same surface, forming a glassy layer. Note that gloss
patination can happen both on freshly broken flint surfaces, and
also on surfaces that have already been porously patinated in the
way described earlier.
The redeposited layer consists of amorphous silica, which is
opal, and if it is of any appreciable thickness it has the
characteristic look of opal – a milky, pearly sheen. Shown right
is a Mesolithic tranchet adze that shows some porous paintination
plus opalescent gloss patination.
A relatively recent, Neolithic struck flint, may, depending
on the circumstances of its burial in the ground, and the type of
material it comes into contact with, show little or no porous
patination and only a very small amount of gloss patination. Below
right is a neolithic flint that shows this.
is an example of a humanly worked flint (a Palaeolithic
biface) that has been patinated with a porous cortex, stained
brown by iron minerals dissolved in ground waters but also with a
glossy patina, probably through surface redeposition of dissolved
silica. Notice that scratches caused by soil creep penetrate
through the glossy layer but not the brown-stained porous patina
Four stages of patination in Mesolithic flint flakes
Some freshly broken flint is almost black. This flake is fresh as
the day it was struck
Here the patination process has just begun - the flint
is turning a dark grey
This flake has assumed a light grey colour and an almost milky
This flake, found in chalky ground, Has been patinated a
uniform white colour
Rust-like spots sometimes form on the ridges of patinated
flints. They are known as 'iron-mould'.
Patina stained brown by Iron minerals
A Mesolithic tranchet adze that shows mainly
Neolithic flake showing only slight gloss