In archaeology, in particular of the Stone Age, lithic reduction is the process of fashioning stones or rocks from their natural state into tools or weapons by removing some parts. 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. In some cases solid rock or larger boulders may be quarried and broken into suitable smaller pieces, and in others the starting point may be a piece of the debitage, a flake removed from a previous operation to make a larger tool. The selected piece is called the lithic core (also known as the "objective piece"). A basic distinction is that between flaked or chipped stone, the main subject here, and ground stone objects made by grinding. 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. 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, 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. 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; for these stones this process is called knapping. 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. Controlled experiments may be performed using glass cores and consistent applied force in order to determine how varying factors affect core reduction.
It has been shown that stages in the lithic reduction sequence may be misleading and that a better way to assess the data is by looking at it as a continuum. The assumptions that archaeologists sometimes make regarding the reduction sequence based on the placement of a flake into a stage can be unfounded. For example, a significant amount of cortex can be present on a flake taken off near the very end of the reduction sequence. 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 when they have a feather termination. These flakes can be used directly as tools or modified into other utilitarian implements, such as spokeshaves and scrapers.
By understanding the complex processes of lithic reduction, archaeologists recognize that the pattern and amount of reduction contribute tremendous effect to lithic assemblage compositions. One of the measurements is the geometric index of reduction. There are two elements in this index: 't' and 'T'. The 'T' is the 'height' of maximum blank thickness and the 't' is the height of retouched scar from the ventral surface. The ratio between t and T is the geometric index of reduction. In theory this ratio shall range between 0 and 1. The bigger the number is the larger amount of lost weight from lithic flake. By using a logarithmic scale, a linear relationship between the geometric index and the percentage of original flake weight lost through retouch is confirmed. 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. For example, Kuhn's geometric index of unifacial reduction (GIUR), which describes the ratio of scar height relative to the flake thickness, is highly influenced by the morphology of the flake blank which limits the applicability of this reduction index.
Alongside the various percussion and manipulation techniques described below, there is evidence that heat was at least sometimes used. Experimental archaeology has demonstrated that heated stones are sometimes much easier to flake, with larger flakes being produced in flint, for example. In some cases the heating changes the colour of the stone.
Percussion reduction, or percussion flaking, refers to removal of flakes by impact. 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. Alternatively, the objective piece can also be struck between a stationary anvil-stone, known as bipolar percussion. Percussion can also be done by throwing the objective piece at an anvil stone. This is sometimes called projectile 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.
Projectile percussion is so basic as to not be considered a technique. It involves throwing the toolstone at a stationary anvil stone. This method provides virtually no control over how the toolstone will fragment, and therefore produces a great deal of shatter, and few flakes. It is difficult to be sure whether or not this method of lithic reduction was ever a commonplace practice, although noting sharp edges on a broken rock might have led early humans to first recognize the value of lithic reduction.
In bipolar percussion the objective piece of toolstone is placed on an anvil stone, and then the percussion force is applied to the tool stone. Like projectile percussion, the tool stone is likely to shatter, rather than producing a single flake. Unlike projectile percussion, the technique has some degree of control to it. Bipolar percussion is not popular with hobbyists, but there is evidence that bipolar percussion was the preferred way of dealing with certain problems. Bipolar percussion has the benefit of producing many sharp flakes, and triangular pieces of stone which can be useful as drills. Bipolar percussion also does not require the manufacturer to locate a platform before setting to work, and bipolar percussion can produce sharp flakes almost the size of the original piece of tool stone. 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. Bipolar percussion is often used to break open small cobbles, or to have a second chance with spent lithic cores, broken bifaces, and tools that have been reworked so much that it is impossible to make further useful tools using traditional lithic reduction. The end result of bipolar percussion is often a big mess, with only a few pieces that can be useful as cores or flakes for further working, but if other methods would result in a total dead-end, bipolar percussion may be desirable.
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. The characteristics of bipolar reduction are different from that occurring in conchoidal fracture and are therefore often misinterpreted by archaeologists and lithic experts.
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.
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.
Soft-hammer percussion involves the use of a billet, usually made of wood, bone or antler as the percussor. These softer materials are easier to shape than stone hammers, and therefore can be made into more precise tools. Soft hammers also deform around the sharp edges of worked stone, rather than shattering through them, making it desirable for working tool stone that already has been worked to some degree before. Soft hammers of course also do not have as much force behind them as hard hammers do. Flakes produced by soft hammers 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. As well as this, soft-hammers can produce longer flakes which aid in the conservation of materials because they produce a longer cutting edge per unit of mass lost.
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. A bending fracture can be produced with a hard hammer. 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 striking platform has separated from the objective piece.
Indirect percussion involves the use of a punch and hammer. The punch and hammer make it possible to apply large force to very small areas of a stone tool. Indirect percussion is therefore often used to achieve detail work on smaller tools. Some modern hobbyists make use of indirect percussion almost exclusively, with little or no pressure flaking to finish their work.
Since indirect percussion can be so precisely placed, the platform is often much smaller on flakes produced in this way than in other methods of flake removal. Of course, indirect percussion requires two hands to hold the percussing tool set. One holds the hammer, and one holds the punch. Therefore, modern hobbyists must use a third object in order to hold the targeted piece of tool stone while they strike it. Often, some sort of clamp or vise is used. No evidence for such devices has yet been found in the archaeological record, but this is partly because they would normally be made of perishable materials, and partly because they can have great variation in design.
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. The process also involves frequent preparation of the edge to form better platforms for pressing off flakes. This is usually accomplished with abraiders 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.
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", was based upon the earliest evidence previously available, which derived from findings of the Upper Paleolithic Solutrean culture in France and Spain.
A blank is a stone of suitable size and shape to be worked into a stone tool. 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. Blanks might be stones or cobbles, just as natural processes have left them, or might be quarried pieces, or flakes that are debitage from making another piece. Whatever their origin, on most definitions no further steps have yet been taken to shape them, or they become a preform.
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. Preforms might also be transported or traded. 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 an incomplete projectile point.
In archaeology, a blade is a type of stone tool created by striking a long narrow flake from a stone core. This process of reducing the stone and producing the blades is called lithic reduction. Archaeologists use this process of flintknapping to analyze blades and observe their technological uses for historical peoples.
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 (outer) side. It is important to note that blade cores appear and are different from regular flaking cores, as each core's conchoidal nature is suited for different types of flaking. Blades are created using stones that have a cryptocrystalline structure and easily be fractured into a smooth piece without fracturing. Blades became the favored technology of the Upper Palaeolithic era, although they are occasionally found in earlier periods. Different techniques are also required for blade creation; a soft punch or hammerstone is necessary for creating a blade.
The long sharp edges of blades made them useful for a variety of purposes. After blades are flaked, they are often incorporated as parts of larger tools, such as spears. Other times, the simple shape and sharpness serves the designed role. Blades were often employed in the impression process of material culture, assisting ancient humans in imprinting ornate designs into other parts of their material culture. Scrapers, used for hide working or woodworking, or burins, used for engraving, are two common such examples.
Cores from which blades have been struck are called blade cores and the tools created from single blades are called blade tools. Small examples (under 12 mm) are called microblades and were used in the Mesolithic as elements of composite tools. Blades with one edge blunted by removal of tiny flakes are called backed blade. A blade core becomes an exhausted core when there are no more useful angles to knock off blades.
Blades can be classified into many different types depending on their shape and size. Archaeologists have also been known to use the microscopic striations created from the lithic reduction process to classify the blades into specific types. Once classified archaeologists can use this information to see how the blade was produced, who produced it, and how it was used.Burin (lithic flake)
In the field of lithic reduction, a burin (from the French burin, meaning "cold chisel" or modern engraving burin) is a type of handheld lithic flake with a chisel-like edge which prehistoric humans used for engraving or for carving wood or bone.
Burins exhibit a feature called a "burin spall", in which toolmakers strike a small flake obliquely from the edge of the burin flake in order to form the graving edge.Cortex (archaeology)
In lithic analysis in archaeology the cortex is the outer layer of rock formed on the exterior of raw materials by chemical and mechanical weathering processes. It is often recorded on the dorsal surface of flakes using a three class system: primary, secondary, and tertiary. The amount of cortex present on artifacts in an archaeological assemblage may indicate the extent of lithic reduction that has occurred. Primary, secondary, and tertiary designations for flakes are generally determined by relative amounts of cortex presented on the dorsal surface. Some archaeologists classify flakes with no cortex as tertiary, flakes with some cortex as secondary, and flakes with all cortex as primary, whereas others may distinctions at every third or half of the dorsal surface covered. Differences in how archaeologists classify the amount of cortex and the results of experimental archaeological tests demonstrating moderate correlation between amount of cortex and stage of reduction, have limited the validity of assumptions based on amount of cortex solely.Debitage
Debitage is all the material produced during the process of lithic reduction and the production of chipped stone tools. This assemblage includes, but is not limited to, different kinds of lithic flakes and lithic blades, shatter and production debris, and production rejects.Eraillure
In lithic analysis (a subdivision of archaeology), an eraillure is a 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. The mechanics of eraillure formation are related to the propagation of a Hertzian cone of force through the cryptocrystalline matrix of the stone, but the particulars are poorly understood. Eraillures usually form only when a hammerstone is used for lithic reduction, and then only occasionally; use of 'soft' hammer fabricators made from bone, antler, and wood produce different flake characteristics but may also produce an eraillure in rare cases.Flake tool
In archaeology, a flake tool is a type of stone tool that was used during the Stone Age that was created by striking a flake from a prepared stone core.
People during prehistoric times often preferred these flake tools as compared to other tools because these tools were often easily made, could be made to be extremely sharp & could easily be repaired. Flake tools could be sharpened by retouch to create scrapers or burins. These tools were either made by flaking off small particles of flint or by breaking off a large piece and using that as a tool itself. These tools were able to be made by this "chipping" away effect due to the natural characteristic of stone. Stone is able to break apart when struck near the edge. Flake tools are created through flint knapping, a process of producing stone tools using lithic reduction. Lithic reduction is the removal of a lithic flake from a larger stone in order to reach the desired tool shape and size. The beginning stone is called the flake lithic core. There are three steps to lithic reduction:
Hard hammer percussion is the first step. It involves knocking off the larger flakes to achieve the desired lithic core for the flake tool. In using hard hammer percussion the flake tools were made by taking metamorphic or igneous rock such as granite or quartz and striking it against the stone. This method was often used to flake large core flakes of hard rock.
Soft hammer percussion is the second step. It involves using a hammer made of bone, which was often antler, in order to knock off flakes from the lithic core. Animal antlers such as moose, deer and elk were often the most common ones used. It allows the user more control over the size and shape of the flakes knocked off. Soft hammer percussion was also used when the stone was more brittle.
Pressure flaking is the final step. It involves using a piece of bone, antler, or piece of hardwood in order to have more control of the flakes knocked off of the lithic core. One simply applies outward and downward pressure to achieve the final flake tool.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. This technology was of major importance to prehistoric cultures before the age of metalworking.Hertzian cone
A Hertzian cone is the cone produced when an object passes through a solid, such as a bullet through glass. More technically, it is a cone of force that propagates through a brittle, amorphous or cryptocrystalline solid material from a point of impact. This force eventually removes a full or partial cone in the material. This is the physical principle that explains the form and characteristics of the flakes removed from a core of tool stone during the process of lithic reduction.
This phenomenon is named after the German physicist Heinrich Rudolf Hertz, who first described this type of wave-front propagation through various media.
Although it might not be agreed by all, natural phenomena which have been grouped with the Hertzian cone phenomena include the crescentic "chatter marks" made on smoothed bedrock by glacial ice dragging along boulders at its base, the numerous crescentic impact marks sometimes seen on pebbles and cobbles, and the shatter cones found at bolide impact sites. James Byous, working independently (at privately funded Dowd Research, Savannah, Georgia USA) has made a protracted study of Hertzian cones. Some of his work may be found via sharing points or directly at Dowd Research. He has produced a comprehensive glossary on Hertzian fractures and related terms. A Hertzian cone is often 104 degrees when created by an indenter. Smaller cones may be produced due to lack of size of the material, or irregularities in the structure of the material. However, in ballistics the faster the projectile the steeper the edges and angle of the cone.Knapping
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. The original Germanic term "knopp" meant strike, shape, or work, so it could theoretically have referred equally well to making a statue or dice. Modern usage is more specific, referring almost exclusively to the hand-tool pressure-flaking process pictured.Levallois technique
The Levallois technique (IPA: [lə.va.lwa]) is a name given by archaeologists to a distinctive type of stone knapping developed by precursors to modern humans during the Palaeolithic period.
It is named after nineteenth-century finds of flint tools in the Levallois-Perret suburb of Paris, France. The technique was more sophisticated than earlier methods of lithic reduction, involving the striking of lithic flakes from a prepared lithic core. A striking platform is formed at one end and then the core's edges are trimmed by flaking off pieces around the outline of the intended lithic flake. This creates a domed shape on the side of the core, known as a tortoise core, as the various scars and rounded form are reminiscent of a tortoise's shell. When the striking platform is finally hit, a lithic flake separates from the lithic core with a distinctive plano-convex profile and with all of its edges sharpened by the earlier trimming work.
This method provides much greater control over the size and shape of the final flake which would then be employed as a scraper or knife although the technique could also be adapted to produce projectile points known as Levallois points. Scientists consider the Levallois complex to be a Mode 3 technology, as a result of its diachronic variability. This is one level superior to the Acheulean complex of the Lower Paleolithic.Lithic
Lithic may refer to:
Relating to stone tools
Lithic analysis, the analysis of stone tools and other chipped stone artifacts
Lithic core, the part of a stone which has had flakes removed from it
Lithic flake, the portion of a rock removed to make a tool
Lithic reduction, the process of removing flakes from a stone to make a tool
Lithic technology, the array of techniques to produce tools from stone
Lithic fragment (geology), pieces of rock, eroded to sand size, and now sand grains in a sedimentary rock
Lithic sandstone, sandstone with a significant component of (above) lithic fragments
Lithic stage, the North American prehistoric period before 10,000 years agoLithic analysis
In archaeology, lithic analysis is the analysis of stone tools and other chipped stone artifacts using basic scientific techniques. At its most basic level, lithic analyses involve an analysis of the artifact’s morphology, the measurement of various physical attributes, and examining other visible features (such as noting the presence or absence of cortex, for example).
The term 'lithic analysis' can technically refer to the study of any anthropogenic (human-created) stone, but in its usual sense it is applied to archaeological material that was produced through lithic reduction (knapping) or ground stone. A thorough understanding of the lithic reduction and ground stone processes, in combination with the use of statistics, can allow the analyst to draw conclusions concerning the type of lithic manufacturing techniques used at a prehistoric archaeological site. For example, they can make certain equation between each the factors of flake to predict original shape. These data can then be used to draw an understanding of socioeconomic and cultural organization.
The term knapped is synonymous with "chipped" or "struck", but is preferred by some analysts because it signifies intentionality and process. Ground stone generally refers to any tool made by a combination of flaking, pecking, pounding, grinding, drilling, and incising, and includes things such as mortars/metates, pestles (or manos), grinding slabs, hammerstones, grooved and perforated stones, axes, etc., which appear in all human cultures in some form. Among the tool types analyzed are projectile points, bifaces, unifaces, ground stone artifacts, and lithic reduction by-products (debitage) such as flakes and cores.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 as a hammerstone. The core is marked with the negative scars of these flakes. The surface area of the core which received the blows necessary for detaching the flakes is referred to as the striking platform. The core may be discarded or shaped further into a core tool, such as can be seen in some types of handaxe.
The purpose of lithic reduction may be to rough out a blank for later refinement into a projectile point, knife, or other stone tool, or it may be performed in order to obtain sharp flakes, from which a variety of simple tools can be made. Generally, the presence of a core is indicative of the latter process, since the former process usually leaves no core. Because the morphology of cores will influence the shape of flakes, by studying the core surface morphology, we might be able to know more information about the dimensional flake attribute, including their length and thickness. Cores may be subdivided into specific types by a lithic analyst. Type frequencies, as well as the general types of materials at an archaeological site, can give the lithic analyst a better understanding of the lithic reduction processes occurring at that site.
Lithic Cores may be multidirectional, conical, cylindrical, biconical, or bifacial. A multidirectional core is the product of any random rock, from which flakes were taken based on the geometry of the rock in any pattern until no further flakes could be removed. Often, multidirectional cores are used in this way until no obvious platforms are present, and then are reduced through bipolar reduction, until the core itself is too small to produce useful flakes. Conical cores have a definite pattern. One flake was removed from a narrow end of the tool stone, and this was then used as the platform to take flakes off in a unifacial fashion all around the edge of the rock. The end result is a cone-like shape. Cylindrical lithic cores are made in a similar fashion, but there is a platform on both ends of the toolstone, with flakes going up and down the side of the cylinder from either direction.
Biconical cores have several platforms around the edge of the stone, with flakes taken alternately from either side, resulting in what looks like a pair of cones stuck together at the bases.Bifacial cores are similar to biconical cores, except that instead of forming a pair of cones, the flakes are taken off in such a way that the core itself grows thinner, without the edges shrinking much. Bifacial cores are usually further reduced into trade bifaces, biface blanks, or bifacial tools. Bifacial cores have been recognized as a technology allowing for efficient material usage(specifically in the creation of edge scrapers) and for their suitability for highly mobile hunter gatherer groups in need of tools made of high quality lithic materials.Lithic flake
In archaeology, a lithic flake is a "portion of rock removed from an objective piece by percussion or pressure," and may also be referred to as a chip or spall, or collectively as debitage. The objective piece, or the rock being reduced by the removal of flakes, is known as a core. Once the proper tool stone has been selected, a percussor or pressure flaker (e.g., an antler 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) producing a Hertzian cone 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 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.Lunate
Lunate is a crescent or moon-shaped microlith. In the specialized terminology of lithic reduction, a lunate flake is a small, crescent-shaped flake removed from a stone tool during the process of pressure flaking.
In the Natufian period, a lunate was a small crescent-shaped stone tool that was sometimes used to harvest grasses.
In archaeology a lunate is a small stone artifact, that has a blunt straight edge and a sharpened crescent shaped back.
The word originates from the Latin word lunatus which means to bend like a crescent, and from luna meaning moon in Latin.
A lunate object can be typically used as a decorative piece or as a stone tool.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. Types of striking platforms include:
Cortex, which consists of an area of cortex used as a platform during initial reduction;
Single-faceted, consisting of a flat platform at right angles to the dorsal surface of the flake and most often associated with conchoidal fractures;
Double-faceted, a variety of multifaceted, prepared platform, also characteristically flat and associated with conchoidal fractures;
Multifaceted, with three or more facets to the platform;
Lipped, a platform type resulting from soft hammer biface reduction; and
Crushed, which occurs when the platform was crushed beyond easy recognition by the detachment blow.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 (Andrefsky 1998:18). Common types include:
Step/snap termination – these occur when a flake snaps or breaks during removal, resulting in an abrupt right-angle break.
Hinge termination – results when the applied force rolls away from the core or objective piece, creating a rounded or blunted distal end.
Overshot/outrepasse/plunging termination - occurs when the applied force dips and removes a section of the opposite margin of the artifact or the distal end of the core. Also referred to as a reverse hinge termination.
Perverse termination - "twisting" breaks resulting from when the applied force is redirected through the material in a helical fashion;
Feather/monotomic termination – a smooth termination that results in a feathered distal end. The distal ends of these flakes are only a few molecules thick, are extremely sharp, and indicate a flawless detachment. These are the intended results of some lithic reduction techniques, and are very desirable for opportunistic tool use that does not require retouching or sharpening.Tool stone
In archaeology, a tool stone is a type of stone that is used to manufacture stone tools,
or stones used as the raw material for tools.Generally speaking, tools that require a sharp edge are made using cryptocrystalline materials that fracture in an easily controlled conchoidal manner.
Cryptocrystalline tool stones include flint and chert, which are fine-grained sedimentary materials; rhyolite and felsite, which are igneous flowstones; and obsidian, a form of natural glass created by igneous processes. These materials fracture in a predictable fashion, and are easily resharpened. For more information on this subject, see lithic reduction.
Large-grained materials, such as basalt, granite, and sandstone, may also be used as tool stones, but for a very different purpose: they are ideal for ground stone artifacts. Whereas cryptocrystalline materials are most useful for killing and processing animals, large-grained materials are usually used for processing plant matter. Their rough faces often make excellent surfaces for grinding plant seeds. With much effort, some large-grained stones may be ground down into awls, adzes, and axes.Yuha Desert
The Yuha Desert is a section of the Sonoran Desert located in the Imperial Valley of California; south of Interstate 8, west of El Centro, and north of the international border.
Unique aspects of the Yuha Desert include the Oyster Shell Beds, De Anza Historical Monument, Crucifixion Thorn Natural Area, and the Yuha geoglyph. It is the homeland of the Kamia, also spelled Kumeyaay, and may have been used by other Native American groups such as the Cahuilla, Quechan, and Cocopah Native American people.
The Yuha Desert is designated an Area of Critical Environmental Concern by the Bureau of Land Management and is managed by the agency as a limited use area for biologic and archaeological resource conservation. The primary species of concern is the flat-tailed horned lizard. Off highway vehicles are limited to signed routes to protect both the flat-tail horned lizard habitat and the archaeological resources including prehistoric campsites and lithic reduction sites along the former edges of Lake Cahuilla, as well as sites representing the use of the region within the historic era.