Lithic reduction
It has been intensely studied and many archaeological industries are identified almost entirely by the lithic analysis of the precise style of their tools and the chaîne opératoire of the reduction techniques they used.
Normally the starting point is the selection of a piece of tool stone that has been detached by natural geological processes, and is an appropriate size and shape.
Flaked stone reduction involves the use of a hard hammer percussor, such as a hammerstone, a soft hammer fabricator (made of wood, bone or antler), or a wood or antler punch to detach lithic flakes from the lithic core.
Lithic reduction may be performed in order to obtain sharp flakes, of which a variety of tools can be made, or to rough out a blank for later refinement into a projectile point, knife, or other object.
As these materials lack natural planes of separation, conchoidal fractures occur when they are struck with sufficient force; for these stones this process is called knapping.
By using a logarithmic scale, a linear relationship between the geometric index and the percentage of original flake weight lost through retouch is confirmed.
[4] In choosing a reduction index, it is important to understand the strengths and weaknesses of each method, and how they fit to the intended research question, as different indices provide different levels of information.
[7] The methods used are: Generally, a core or other objective piece, such as a partially formed tool, is held in one hand, and struck with a hammer or percussor.
[7] Percussors are traditionally either a stone cobble or pebble, often referred to as a hammerstone, or a billet made of bone, antler, or wood.
The lack of control makes bipolar percussion undesirable in many situations, but the benefits mean that it often has a use, especially if workable material is rare.
An alternative view of the bipolar reduction technique is offered by Jan Willem Van der Drift which contradicts the suggestion that there is little control over fracturing.
This method of manufacture is believed to have been used to make some of the earliest stone tools ever found, some of which date from over 2 million years ago.
[14] In most cases, the amount of pressure applied to the objective piece in soft-hammer percussion is not enough for the formation of a typical conchoidal fracture.
This method provides virtually no control over how the toolstone will fragment, and therefore produces a great deal of shatter, and few flakes.
The punch and hammer make it possible to apply large force to very small areas of a stone tool.
Copper retoucheurs to facilitate this process were widely employed in the Early Bronze Age – and may therefore be associated with Beaker Culture in northwestern Europe.
Occasionally, outrepasse breaks occur when the force propagates across and through the tool in such a way that the entire opposite margin is removed.
An archaeological discovery in 2010 in Blombos Cave, South Africa, places the use of pressure flaking by early humans to make stone tools back to 73,000 BCE, 55,000 years earlier than previously accepted.
Blanks are the starting point of a lithic reduction process, and during prehistoric times were often transported or traded for later refinement at another location.
[21] The next stage creates a preform, or roughly shaped piece of stone, that probably reveals the final form of the tool, but is not complete.
Larger and thicker than the intended tool, it lacks the final trimming and refinement that is present in the completed artifact.
