Technology and Terminology of Knapped Stone - IRIT

2. Knappin g suitability o f hard rocks
One should bear in mind that experimentation witnesses constant breakthroughs, and that
the assessment of rocks' suitability for knapping progresses accordingly. Nevertheless, although
we are perforce guided by what we currently know, our assessment of the knapping suitability
of a particular rock must absolutely be based on experimental tests.
2.1. A n experimenter' s viewpoin t
Prehistoric people worked all the raw materials at their disposal, testing, selecting and
choosing them according to their knapping suitability, their abundance and their shape.
The following presentation of raw materials takes absolutely no account of mineralogical
or petrographical classifications; it is based solely on the knapping characteristics of different
rock types, appreciated in the course of experimental tests. The viewpoint of a single experimenter
could well be considered empirical. However, allowances made for minor details, most
modern stone-knappers come to similar conclusions, even though some of them may attain a
higher degree of proficiency in certain techniques and methods.
The opinions professed here concerning a few dozen materials are therefore those of a
single experimenter, whose motivations differ from prehistoric man's. This does not purport to
be a comprehensive survey of the question, for the varieties of rocks knapped by prehistoric
workers are countless.
One of the authors (J.T.) has applied the principle of trying out every conceivable
technique on as many natural materials as possible (pressure and percussion debitage and
retouching, using stone, bone, wood, antler, ivory, etc.); this led to many attemps, which were
not however pursued over a long period of time. At the moment, we are far from having
exhausted all the possibilities of systematic experimentation to further our understanding of
knapped tools.
We shall not re-examine the physical qualities that cause a material to be good or bad,
such as elasticity, homogeneity or fragility 21
. What we offer is a basic global appreciation,
bearing in mind however that homogeneity is the main prerequisite for regular debitage (as in
standardized blade production, for instance) or long retouches.
As a matter of fact, rocks can be placed on a continuum, and range from those with which
"anything is possible" to those from which flakes can only be removed with difficulty. In order
to clarify by simplifying, we propose three grades of suitability for knapping.
• Rocks that are very easy to work. These fall into two main categories : vitreous and
fragile rocks, such as obsidian; non-vitreous and moderately fragile rocks, such as certain flints.
• Rocks that are quite easy to work.
• Rocks that are difficult to work.
These three grades are shown in the table (fig. 2), as well as those resulting from heat
treatment; it seemed both convenient and effective to thus sum up experiments for the
manufacure of:
- leaf-shaped bifacial pieces by percussion with a soft hammer;
- blades by direct percussion with a soft hammer, or by indirect percussion;
- blades by pectoral pressure with a crutch;
- long parallel retouches by pressure.
These appreciations must however be qualified.
• The properties of some rocks may allow the application of certain techniques, while
few good results, if any, will be achieved when other techniques are applied. For instance, very
good handaxes, or even good thin leaf-shaped bifacial pieces, can be made from sanukite, a
variety of andesite from Japan. On the other hand, the removal of flakes proves difficult, and the
extraction of blades by percussion is virtually impossible.
• A very few rocks require flaking "with the grain". For instance, the fossil wood from
Tidikelt, in the Algerian Sahara, is much more easily worked if debitage follows the veins (fibres,
in fact), which are still apparent - and that is precisely what the Aterians did.
21 Crabtree, 1967.
21