Lithic reduction


Lithic reduction

Lithic reduction involves the use of a hard hammer precursor, 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 a lump of tool stone called a lithic core (also known as the "objective piece"). As flakes are detached in sequence, the original mass of stone is reduced; hence the term for this process. Lithic reduction may be performed in order to obtain sharp flakes, on 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. Flakes of regular size that are at least twice as long as they are broad are called blades. Lithic tools produced this way may be bifacial (exhibiting flaking on both sides) or unifacial (exhibiting flaking on one side only).

Cryptocrystalline or amorphous stone such as chert, flint, obsidian, and chalcedony, as well as other fine-grained stone material, such as rhyolite, felsite, and quartzite, were used as a source material for producing stone tools. As these materials lack natural planes of separation, conchoidal fractures occur when they are struck with sufficient force. The propagation of force through the material takes the form of a Hertzian cone that originates from the point of impact and results in the separation of material from the objective piece, usually in the form of a partial cone, commonly known as a lithic flake. This process is predictable, and allows the flintknapper to control and direct the application of force so as to shape the material being worked.

Removed flakes exhibit features characteristic of conchoidal fracturing, including striking platforms, bulbs of force, and occasionally eraillures (small secondary flakes detached from the flake's bulb of force). Flakes are often quite sharp, with distal edges only a few molecules thick, and can be used directly as tools or modified into other utilitarian implements, such as spokeshaves and scrapers.

Contents

Techniques

Percussion reduction

Percussion reduction, or percussion flaking, refers to removal of flakes by striking a core or other objective piece, such as a partially formed tool, with a hammer or percussor. Alternatively, the objective piece can also be struck against a stationary anvil-stone, known as bipolar percussion. Percussors are traditionally either a stone cobble or pebble, often referred to as a hammerstone, or a billet made of bone, antler, or wood. Often, flakes are struck from a core using a punch, in which case the percussor never actually makes contact with the objective piece. This technique is referred to as indirect percussion.[1]

An example of hard hammer percussion.

Hard-hammer percussion

Hard hammer techniques are generally used to remove large flakes of stone. Early flintknappers and hobbyists replicating their methods often use cobbles of very hard stone, such as quartzite. This technique can be used by flintknappers to remove broad flakes that can be made into smaller tools. 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.[2]

It is the use of hard-hammer percussion that most often results in the formation of the typical features of conchoidal fracture on the detached flake, such as the bulb of percussion and compression rings.[3]

An example of soft hammer percussion

Soft-hammer percussion

Soft-hammer percussion involves the use of a billet, usually made of wood, bone or antler as the percussor. Flakes produced in this manner are generally smaller and thinner than those produced by hard-hammer flaking; thus, soft-hammer flaking is often used after hard-hammer flaking in a lithic reduction sequence to do finer work.[4]

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. Rather, soft-hammer flakes are most often produced by what is referred to as a bending fracture, so-called because the flake is quite literally bent or "peeled" from the objective piece. Flakes removed in this manner lack a bulb of percussion, and are distinguished instead by the presence of a small lip where the flake's stiking platform has separated from the objective piece.[5]

Pressure flaking

An example of pressure flaking

Pressure flaking is a method of trimming the edge of a stone tool by removing small lithic flakes by pressing on the stone with a sharp instrument rather than striking it with a percussor. This method, which often uses punches made from bone or antler tines (or, among modern hobbyists, copper punches or even nails), provides a greater means of controlling the direction and quantity of the applied force than when using even the most careful percussive flaking. 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.

Usually, the objective piece is held clasped in the flintknapper's hand, with a durable piece of fabric or leather protecting the flintknapper's palm from the sharpness of the flakes removed. The tip of the flaking tool is placed against the edge of the stone tool and pressed hard, removing a small linear or lunate flake from the opposite side. In some instances, a hammer and punch is used while the tool is held down with a vise. The process also involves frequent preparation of the edge to form better platforms for pressing off flakes. This is usually accomplished with abraders made from a coarse-grained stone such as basalt or quartzite. Great care must be taken during pressure flaking so that perverse fractures that break the entire tool do not occur. Occasionally, outrepasse breaks occur when the force propagates across and through the tool in such a way that the entire opposite margin is removed.[6]

The use of pressure flaking facilitated the early production of sharper and more finely detailed tools. Pressure flaking also gave toolmakers the ability to create notches where the objective piece could be bound more securely to the shaft of the weapon or tool and increasing the object's utility.

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. The previously accepted date, "no more than 20,000 years ago",[7] was based upon the earliest evidence previously available, which derived from findings of the Upper Paleolithic Solutrean culture in France and Spain.[8]

Blank

A blank is a thick, shaped stone biface of suitable size and configuration for refining into a stone tool. Blanks are the beginning products of lithic reduction, and during prehistoric times were often created for trade or later refinement at another location. Blanks were often formed through the initial reduction of lumps of tool stone at simple quarries, often no more than easily accessible outcroppings of the local tool stone (although this was certainly not the case at Grimes Graves in England). Sometimes the shape of the blank hints at the shape of the final tool it will become, but this is not always the case. A blank may consist of either a large, unmodified flake or a reduced core, often with a rough subtriangular or lanceolate shape. Rough chopping tools, derived by removing a few flakes along one edge of the cobble, can also be considered to fall into this group.

Preform

A preform is the rough, incomplete and unused basic form of a stone tool. Typically, a preform is the shaped remnant of a lithic core. Larger and thicker than the intended tool, it lacks the final trimming and refinement that is present in the completed artifact. Sometimes basic features such as stems and notches have been initiated. In most cases, the term refers to incomplete projectile point.

See also

  • Ground stone
  • Lithic analysis
  • Lithic technology
  • Stone Age
  • Waldorf, D.C. (1994) (Paperback). (1993). The Art of Flint Knapping. Fourth Edition. Mound Builder Books, Branson MO, USA. pp. 76.  (Excellent illustrations by Valerie Waldorf of processes, techniques, hand tools, ancient and modern knapped artifacts [mostly North American]. On front and rear cover are photos of precisely made replicas of prehistoric points and within the text are B&W photos including two full-scale [12⅝ inch and 10¾ inch] "Danish dagger" replicas made by the author.)

Notes

  1. ^ Andrefsky 2004:12
  2. ^ Andrefsky 2004:31
  3. ^ Cotterell and Kamminga 1987:986
  4. ^ Cotterell and Kamminga 1987:867
  5. ^ Andrefsky 2005:18–20; Cotterell and Kamminga 1987:690
  6. ^ Cotterell and Kamminga 1987:700–745
  7. ^ "Stone Agers Sharpened Skills 55,000 Years Earlier Than Thought". Wired. 29 October 2010. http://www.wired.com/wiredscience/2010/10/stone-tool-sharpening/. 
  8. ^ Tamar Kahn (29 October 2010). "Scientists Find Earliest Evidence of Method of Shaping Weapons". AllAfrica. http://allafrica.com/stories/201010290156.html. 

References

  • Andrefsky, W. (2005) Lithics: Macroscopic Approaches to Analysis. Cambridge: Cambridge University Press. ISBN 0521615003
  • Cotterell, B. and Kamminga, J. (1987) The Formation of Flakes. American Antiquity 52:675–708

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