Lithic flake

Lithic flake

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In archaeology
Archaeology
Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...

, a lithic flake is a "portion of rock
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

 removed from an objective piece by percussion or pressure," and may also be referred to as a chip or spall
Spall
Spall are flakes of a material that are broken off a larger solid body and can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure...

, or collectively as debitage
Debitage
The term debitage refers to all the waste material produced during lithic reduction and the production of chipped stone tools. This assemblage includes, but is not limited to, different kinds of lithic flakes, shatter, and production errors and rejects....

. The objective piece, or the rock being reduced by the removal of flakes, is known as a core
Lithic core
In archaeology, a lithic core is a distinctive artifact that results from the practice of lithic reduction. In this sense, a core is the scarred nucleus resulting from the detachment of one or more flakes from a lump of source material or tool stone, usually by using a hard hammer percussor such...

. Once the proper tool stone
Tool stone
The term tool stone has multiple meanings.In archaeology, a tool stone is a type of stone that is used to manufacture stone tools.Alternatively, the term can be used to refer to stones used as the raw material for tools....

 has been selected, a percussor or pressure flaker (e.g. an antler
Antler
Antlers are the usually large, branching bony appendages on the heads of most deer species.-Etymology:Antler originally meant the lowest tine, the "brow tine"...

 tine) is used to direct a sharp blow, or apply sufficient force, respectively, to the surface of the stone, often on the edge of the piece. The energy of this blow propagates through the material, often (but not always
Termination type
In lithic reduction, termination type is a characteristic indicating the manner in which the distal end of a lithic flake detaches from a core...

) producing a Hertzian cone
Hertzian cone
A Hertzian cone is the cone of force that propagates through a brittle, amorphous or cryptocrystalline solid material from a point of impact, eventually removing a full or partial cone. An example often occurs when a plate-glass window is struck by a small object, such as an airgun projectile...

 of force which causes the rock to fracture in a controllable fashion. Since cores are often struck on an edge with a suitable angle (x<90°) for flake propagation, the result is that only a portion of the Hertzian cone is created. The process continues as the flintknapper
Flintknapper
Knapping is the shaping of flint, chert, obsidian or other conchoidal fracturing stone through the process of lithic reduction to manufacture stone tools, strikers for flintlock firearms, or to produce flat-faced stones for building or facing walls, and flushwork decoration.- Method :Flintknapping...

 detaches the desired number of flakes from the core, which is marked with the negative scars of these removals. The surface area of the core which received the blows necessary for detaching the flakes is referred to as the striking platform
Striking platform
In lithic reduction, the striking platform is the surface on the proximal portion of a lithic flake on which the detachment blow fell; this may be natural or prepared...

.

Production



Flakes may be produced by a variety of means. Force may be introduced by direct percussion (striking the core with a percussor such as a rock or antler), indirect percussion (striking the core with an object, sometimes referred to as a "punch," which itself is struck by a percussor, similar to the use of a hammer and chisel to shape stone), or by pressure. Additionally, flakes may be initiated in a Hertzian, bending, or wedging fashion. When a flake is detached from its core in a Hertzian fashion, the flake propagates in a conchoidal manner from the point of impact or pressure, usually producing a partial Hertzian cone. The cone of force often leaves a distinctive bulb of applied force
Bulb of applied force
In lithic analysis, a subdivision of archaeology, a bulb of applied force is a defining characteristic of a lithic flake...

 on the flake and a corresponding flake scar on the core. A bending initiation results when a flake initiates not at the point where the force was applied, but rather further away from the edge of the core, resulting in a flake with no Hertzian cone or bulb of applied force and few if any of the characteristics ripples or undulations seen on the ventral surface of conchoidally produced flakes. Wedging initiation is the result of a strong hammer blow. At impact, concenctric radii emanate from the point of percussion, but unlike conchoidal fracture, the force travels along what would be the center of the Hertzian cone. The bipolar reduction technique is typified by its use of wedge initiation. Like bending initiation, no bulb of applied force results from wedging initiation, although in the bipolar technique, flakes may appear to have two points of percussion, on opposite ends, due to the fact that the core has been fractured by a hammer and anvil technique. The core is placed on a hard surface or "anvil" and is struck above by a hammer, thus the fracture may propagate from both ends simultaneously.

The end which received the blow or pressure is referred to as the proximal end of the flake; the terminal end is referred to as the distal end. The side displaying the bulb of force but without flake scars (barring an errailure flake scar or additional working of the flake) is called the ventral (or interior) surface, while the opposite side, displaying the flake scars of previous removals, or the cortical or original rock surface, is the dorsal (or exterior) surface.

On most natural cobbles or nodules of source material, a weathered outer rind called a cortex covers the unweathered inner material. Flakes are often differentiated by the amount of cortex present on their dorsal surfaces, because the amount of cortex indicates when in the sequence of reduction the flake came from. Primary flakes are those whose dorsal surfaces are entirely covered with cortex; secondary flakes have at least a trace of cortex on the dorsal surface; and tertiary (interior) flakes lack cortex, having derived entirely from the interior of the core. Primary flakes and secondary flakes are usually associated with the initial stages of lithic reduction
Lithic reduction
Lithic reduction involves the use of a hard hammer precursor, such as a hammerstone, a soft hammer fabricator , or a wood or antler punch to detach lithic flakes from a lump of tool stone called a lithic core . As flakes are detached in sequence, the original mass of stone is reduced; hence the...

, while tertiary flakes are more likely to be associated with retouching and bifacial
Biface
In archaeology, a biface is a two-sided stone tool and is used as a multi purposes knife, manufactured through a process of lithic reduction, that displays flake scars on both sides. A profile view of the final product tends to exhibit a lenticular shape...

 reduction activities.

Prominent bulbs of force generally indicate that a hard hammer percussor (hammerstone
Hammerstone
In archaeology, a hammerstone is a hard cobble used to strike off lithic flakes from a lump of tool stone during the process of lithic reduction. The hammerstone is a rather universal stone tool which appeared early in most regions of the world including Europe, India and North America...

) was used to detach the flake; flakes displaying this characteristic are referred to as conchoidal flakes. Hard hammer flakes are indicative of primary reduction strategies (e.g., core reduction, roughing of blanks and preforms, and the like). More moderate and diffuse bulbs may indicate the use of a soft hammer percussor—such as bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

, wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

, or antler
Antler
Antlers are the usually large, branching bony appendages on the heads of most deer species.-Etymology:Antler originally meant the lowest tine, the "brow tine"...

 -- which produces the bending flakes often associated with bifacial
Biface
In archaeology, a biface is a two-sided stone tool and is used as a multi purposes knife, manufactured through a process of lithic reduction, that displays flake scars on both sides. A profile view of the final product tends to exhibit a lenticular shape...

 thinning and trimming. The relative abundance of each type of flake can indicate what sort of lithic work was going on at a particular spot at a particular point in time.

A blade
Blade (archaeology)
In archaeology a blade is a type of stone tool created by striking a long narrow flake from a stone core.Blades are defined as being flakes that are at least twice as long as they are wide and that have parallel or subparallel sides and at least two ridges on the dorsal side...

is defined as a flake with parallel or subparallel margins that is usually at least twice as long as it is wide. There are numerous specialized types of blade flakes. Channel flakes are characteristic flakes caused by the fluting of certain Paleo-Indian projectile point
Projectile point
In archaeological terms, a projectile point is an object that was hafted to a projectile, such as a spear, dart, or arrow, or perhaps used as a knife....

s; such fluting produced grooves in the projectile points which may have facilitated hafting. Prismatic blade
Prismatic blade
In archaeology, a prismatic blade is a long, narrow, specialized lithic flake with parallel margins. Prismatic blades are removed from polyhedral blade cores through pressure reduction. This process results in a very standardized finished tool and waste assemblage...

s are long, narrow specialized blades with parallel margins which may be removed from polyhedral blade cores, another common lithic feature of Paleo-Indian lithic culture. Prismatic blades are often triangular in cross section with several facets or flake scars on the dorsal surface.

Other flake characteristics


The striking platform
Striking platform
In lithic reduction, the striking platform is the surface on the proximal portion of a lithic flake on which the detachment blow fell; this may be natural or prepared...

 is the point on the proximal portion of the flake on which the detachment blow fell or pressure was placed; this may be natural or prepared. Termination type
Termination type
In lithic reduction, termination type is a characteristic indicating the manner in which the distal end of a lithic flake detaches from a core...

 is a characteristic indicating the manner in which the distal end of a flake detached from a core. Flake terminations may be feathered, hinged, stepped, or plunging (also known as overshot or outrepassé). Feathered terminations are often very sharp, as the flake gradually reduces to a very fine thickness before the force exits the core and removes the flake. Hinged terminations are the result of the force rolling away from the core, resulting in a rounded distal end. Step terminations result when a flake prematurely breaks or snaps during removal, leaving a distal end that is often squared off. Plunging flakes are the result of the force rolling back towards the core and often taking off its "bottom." Hinge, step, and plunging terminations are often seen as "errors," and certainly they sometimes were, but they also may be deliberately produced. Eraillure
Eraillure
In lithic analysis , an eraillure is a small secondary flake removed from a lithic flake's bulb of force, which is a lump left on the ventral surface of a flake after it is detached from a core of tool stone during the process of lithic reduction...

s, also referred to as "bulbar scars", are tiny flake scars that appear on some bulbs of applied force. The reason they form is not entirely understood. Of those flakes that do exhibit eraillures, very few have more than one.

Secondary and tertiary flakes display dorsal flake scars, which are simply the markings left behind by flakes detached prior to the detachment of the subject flake. These flake scars are one of the lines of evidence used to infer the method of lithic reduction, or the process by which raw material is turned into useful objects.

Tools


Flakes can be modified into formal tools, which result from additional working of the piece to shape a flake into a desired form, or the they can be used without further modification, and are then referred to as expedient tools. For example scrapers, which may be made by additional removals (retouching) to the edge of a piece, or burin
Burin
Burin from the French burin meaning "cold chisel" has two specialised meanings for types of tools in English, one meaning a steel cutting tool which is the essential tool of engraving, and the other, in archaeology, meaning a special type of lithic flake with a chisel-like edge which was probably...

s, which are created by a burin blow on the tip of a blade which produces a chisel-like edge which may have been used for graving and carving wood or bone.