Pressure Flaking Research Articles

An experimental approach to the study of amber processing in the Neolithic: technical analysis of the Siliņupe amber assemblage, 4 th mill. BC, Latvia

Abstract Amber appears in the archaeological material of the Eastern Baltic region in the Middle Neolithic and continues in intensive use until the end of the Neolithic. Four major amber-working centres are known in the Eastern Baltic, the least studied of which is the settlement of Siliņupe (4th mill. BC). Not yet widely applied in research on Stone Age amber technologies, but very promising, is an analytical approach combining experimental archaeology and traceology to study processing choices made in specific production stages (i. e., individual technological elements), revealing that fine-grained sandstone was favoured for surface grinding, while flint tools were most widely used for shaping and surface treatment, distinguishing three techniques, namely shaving, scraping and pressure flaking, each identifiable by characteristic features. The study suggests that amber and flint processing were largely intertwined, as pressure flaking along with indirect percussion (used for splitting amber) derive from flint processing, and in the case of pressure flaking, required specific know-how.

К ПОСТАНОВКЕ ПРОБЛЕМЫ МАРКЕРОВ КАМЕННЫХ ИНДУСТРИЙ ЭПОХИ ЭНЕОЛИТА И БРОНЗЫ ГОРНО-ЛЕСНОГО ЗАУРАЛЬЯ

The authors propose to discuss the methodology of searching for the defi nitive indicators of flaking techniques of the Eneolithic — Bronze Age in the mountain-forest Trans-Urals. The methodology is based on a step-by-step cross-referencing analysis of raw materials, technological and morphological characteristics of stone artifacts. The multilayer settlement Shaitanskoe 4–6 stone tools assemblage (the Kirovgrad district, Sverdlovsk Oblast) served as the main resource for the analysis. Main stages of the site’s populating correlated with the Eneolithic and the Bronze Age (Cherkaskul culture). Arrowheads were chosen as the key category of artifacts. This choice was based on both the large number of these artifacts (more than 100 items) and their fairly reliable cultural and chronological verification by the well-known interments and single-layer sites of the Urals and the adjacent territories. The Eneolithic flaking technique demonstrated a pronounced variability of tools. Pressure flaking technique used for obtaining blanks of a certain type (blades, microblades, and flakes of preset shapes and sizes) formed the lithic industry basis. During the Bronze Age, the emphasis shifted towards biface-production-oriented striking and counter striking knapping techniques. One of the Bronze Age lithic industry markers was a significant amount of characteristic waste, defected and good blanks as opposed to a small group of two-sided retouched tools with a high level of standardization and manufacturing quality (arrowheads, knives of an asymmetrical triangular shape with an arc-shaped side blade, scrapers of geometric shapes, etc.). The Eneolithic population preferred siliceous and clay shales, high-quality homogeneous jaspers, some types of chalcedony of gray and yellow, homogeneous flint of greenish and greenish-gray shades, and rhyolites of similar colors. During the Bronze Age, most popular materials were mottled flint of mediocre quality, siliceous shales of dark shades, siliceous quartz and chalcedony of light tones, and some varieties of jasper.

The stone industry transformations at the edge of Pleistocene and Holocene: Evidence from the north-western and north-central Caucasus

In this paper, the authors report results of a detailed technological and typological analysis of the Epipalaeolithic assemblages from three stratified sites in the North Caucasus that were excavated in recent years at a modern scientific level with application of sediment water screening, which allowed to obtain numerous microlithic artefacts. The lithic analysis of the assemblages indicates a gradual development in the knapping technology, which resulted in the first application of the pressure flaking technique in the final Epipalaeolithic, and innovations in the tool set, particularly in the assortment of geometric microliths. The authors consider the stone industry transformations at the edge of Pleistocene and Holocene in the context of cultural continuity during the final Epipalaeolithic and up to the beginning of the Holocene in the region.

Каменная индустрия памятника Гвоздевка i

The article covers the exploration of the stone industry of a Mesolithic site Gvozdevka I. The Stone Age man site is located in Moskalenki district of Omsk region, at the southern end of Lake Ebeyty, on the eastern bank of flood plain Amre (Amrinsky beam). It was discovered in 1976, last investigated in 2004. In the course of archaeological work, a representative collection of stone artefacts was formed, among them microplates occupying a considerable place. The manufacturing specificity of site materials is difficult for analysis, but certain aspects of plate production and utilisation can be taken into consideration. The techno-typological method, as part of attributive approach, was used for their analysis. The description and analysis of the stone industry was made according to the parameters characterising the metric indicators of cleavage, cleavage zone and dorsal surface. The basic strategy of stone cleavage is reconstructed, aimed to produce lamellar chipping with the use of pressure flaking technique. The production of inlay blanks - thin plates with straight lateral profile and sharp longitudinal edges - appears to have been the ultimate goal of the cleavage. The quality of the analysed material enables one to study not only the techno-typological aspects of its manufacture, but also the traces of non-utilisation wear, secondary processing of blanks as well as functional wear (which is the subject of further research). This suggests that the monument was used to split pre-nuclei or nuclei brought by people; the obtained plates were actively used in the process of treatment of various materials. On the whole, using the attributive approach to the study of Gvozdevka I site stone industry made it possible to establish the major strategies of stone splitting and to reconstruct the primary splitting system, as well as to create a framework for comparison with other monuments of the same period on the territory of Omsk region and adjacent areas, to outline the prospects for further research.

Middle Stone Age Bifacial Technology and Pressure Flaking at the MIS 3 Site of Toumboura III, Eastern Senegal

Over the past decade, the increasing wealth of new archaeological data on the Middle Stone Age (MSA) in Senegal and Mali has broadened our understanding of West Africa’s contributions to cultural developments. Within the West African sequence, the phase of Marine Isotope Stage 3 (MIS 3, ca. 59-24 ka) yielded so far the best known and extensive archaeological information. The site of Toumboura III encompasses an occupation dated by optically stimulated luminescence (OSL) to between 40 ± 3 ka and 30 ± 3 ka. It provides the largest, well-dated, and stratified lithic assemblage in West Africa for the MSA and sheds light on an unprecedented cultural expression for this period, adding to the notable diversity of the late MSA in this region. We conducted a technological analysis of the lithic components following the chaîne opératoire approach. The lithic assemblage features a prevalence of bifacial technology and the exploitation of flakes as blanks for tool production. The craftspeople manufactured distinct types of bifacial tools, including small bifacial points shaped by pressure technique. The new data from Toumboura III demonstrate behavioral patterns that are entirely new in the region. By revealing behavioral innovations and technological particularities, these results on the techno-cultural dynamics during the MIS 3 phase of the MSA enhance our understanding of the complex Pleistocene population history in this part of Africa.

The Neolithisation of the Adriatic: Contrasting Regional Patterns and Interactions Along and Across the Shores

Abstract The beginning of the Neolithic in the Adriatic region dates back to approximately 6000 cal BC, and the appearance of Impressed Ware pottery marks its generic development. By combining lithic, economic, and paleoenvironmental data, we propose a new arrhythmic model for the chronology of Neolithisation in the Adriatic. On the one hand, the available data suggest that in the south-central part of the basin (Dalmatia and Apulia) the transition to farming was relatively quick, resulting from the colonisation of an open landscape (seemingly linked to the “8.2 ka event” and the onset of a drier climate). These newcomers mostly settled in the fertile plains of the Dalmatian and Apulian hinterlands, basing their subsistence almost exclusively on agriculture and livestock, while lithic blade production in cherts from Gargano (southern Italy) indicates important social aspects and complex management strategies (mining activities, more complex modes of pressure flaking, and specialised distribution networks). However, on the other hand, in the northern Adriatic (Istria, Karst, eastern Po Plain, and Marches), the Neolithic emerged somewhat later, possibly as a result of some form of acculturation. Although available data are still scarce, some evidence suggests that the last Mesolithic groups played an active role in the process of Neolithisation in these areas, where certain Castelnovian traditions have been identified in the lithic production accompanying Impressed Ware (the use of local cherts, lamellar production by indirect percussion, and “simpler” forms of pressure flaking) and in the economy, e.g. importance of fishing.

Confined Pressure Compression Scratches: A New Observation in Lithic Analysis

ABSTRACT During the Late Neolithic in southern Scandinavia and northern Germany, flint daggers reached an exceptionally high quality of craftsmanship. The blades of these daggers were pattern flaked using a pressure technique, which has been replicated by several archaeologists and flint knappers. Observations of scratches caused by the pressure flaking technique can be pointed out on the archaeological finds, and explained as a consequence of the holding position. This grants archaeology a new insight into the techniques of the ancient craftsmen and the interaction between the material and the individual. The “confined pressure compression scratches” suggests that a consistent pressure flaking technique was used throughout the late Neolithic in the region, regardless of the dagger morphology. The observations presented in this article can be extended to other pressure flaked lithics of the world.

Evidence of Absence or Absence of Evidence?

The last hunter-gatherers of the central and western Mediterranean are associated with the Castelnovian technocomplex, which developed during the seventh millennium BC and is characterized mainly by its lithic industries, which reflect important changes that occurred during the Late Mesolithic: debitage from this time is oriented towards blade production by pressure-flaking and the manufacture of special tools, such as trapezes (made by the microburin technique) and notched blades. Although rare, Castelnovian sites have been identified in the wider Adriatic region of south-central Italy, Albania, Montenegro and the Italian and Slovenian Karst. However, it seems that the Croatian coast and its hinterland in the eastern Adriatic lack any traces. No sites were found in Dalmatia and only a few questionable surface finds come from Istria. This study explores whether this absence is due to historical factors, such as depopulation during the Late Mesolithic or the region being outside the Castelnovian expansion route, or whether it is because of a combination of taphonomic causes (such as loss of sites by marine transgression) and lack of previous research. The paper also focuses on the hypothesis that the presence of the last hunter-gatherers can be detected indirectly through the persistence of Castelnovian elements in the oldest Neolithic Impressed Ware assemblages of the eastern Adriatic. I further propose that Castelnovian traits are observable in the Impressed Ware assemblages of Istria. This Mesolithic tradition consists of the use of local flint, blade production by indirect percussion and ‘simpler’ forms of pressure flaking in lithic production, while marine resources remain an important food resource.

Kimberley points of Western Australia: Pressure flaking, projections and prestige

Kimberley points are pressure flaked bifaces with marginal projections, produced within the last millennium, in north Western Australia. These points were hafted for hunting and fighting in recent times, although there is some suggestion that smaller points tended to be hafted for use in favour of larger points, which were reserved for trade and exchange. Kimberley Points are imbued with strong social signalling and prestige qualities, known from Historic times. This paper examines whether these qualities are reflected archaeologically in their marginal projections produced with pressure flaking; and their morphology and production. Multiple sources of Kimberley Point archaeology, ethnography, and production are critically reviewed. As prestige items, the marginal projections are found to very likely relate to their social value, rather than functional drive, which this study investigates using morphological approaches. Samples from both ethnographic collections and archaeological surface assemblages are analysed. The study finds that biface elongation, length and perimeter length each greatly influenced the number of and size of marginal projections, regardless of raw material. This aspect of production probably reflects the value and social prestige for large serrated points, likely produced by the knapper before an audience in virtuoso displays of pressure flaking. It is conceivable that these complex social practices emerged around 1,000 years ago. This study provides a rare glimpse into the social values of stone tool produces, and links archaeological data to social values in the past.

Стратификация керамических комплексов неолита реки Конды

Purpose. Over the past 40 years, dozens of pit-houses, semi-dugouts, above-ground huts, hearth-like structures, and burial grounds have been investigated on the territory of the Konda River basin. Classification of cultural artifacts is based on stylistic attributes and distinctions of ceramics, while chronology rests on conventional 14C dating. At the present stage, one of the most important tasks is to develop the chronology and periodization of the Neolithic sites located in the Konda River basin. The starting point in the solution of this problem should be the multilayer stratified habitation sites. This paper presents the results of the investigation of Mulymya-3 settlement, which is one of such sites. Results. In 2019, early Neolithic stratified complexes were studied in Mulymya-3 settlement. The excavations of the early buildings revealed that among the predominant artifacts of flat-bottomed dishes, there also were layers of Shoushma and Sumpanya type pottery. The stroke-ornamented ware, i. e. flat-bottomed ceramic dishes with collars and rims, were classified as “Mulymya type pottery”. 14C dating of the soot from a flat-bottomed vessel suggested that the site was more or less continuously occupied between 6 690–6 500 cal. BC. Conclusion. The artifacts from Mulymya-3 settlement made it possible to shift the lower boundary of the Neolithic age in the Konda River basin to earlier dates. A typical feature of the earliest period (6 600 / 6 500 – 3 600 / 3 400 cal. BC) is Mulymya, Shoushma, and Umytinsky type pottery characterized by original traditions of ceramic production. The appearance of pottery in the second third of the 7th millennium BC did not affect the traditional economy of taiga societies. The stone-working technique was based on fracturing technologies (percussion flaking, pressure flaking, chipping, splintering), abrasive processing, and battering. In the 6th millennium BC, the people belonging to Shoushma and Umytinsky cultures started contacting with each other, which can be proved by dishes of both types found in the excavated pit-dwelling in similar stratigraphic conditions. Another proof is the appearance of mixed-looking pottery, in particular dishes of the Sumpanya type. From the end of the 6th millennium, the Shoushma pottery traditions were gradually degrading. From that time and until the turn of the 5th–4th millennia BC the Konda River basin was inhabited by the Umytinsky population. It is probable that those were the people who continued the tradition of making flat-bottomed dishes (Satyginsky / Boborykinsky type pottery).

Did heat treatment of flints take place in the Moravian Magdalenian? The case of Balcarka Cave

Six Magdalenian artefacts from Balcarka Cave (Czech Republic) were selected on the basis of their colour or the presence of lustre and analysed for heat-treatment. A combination of methods was used on the basis of past research. Isothermal remanent magnetism (IRM) proved itself to be the most useful method to distinguish potentially heat-treated artefacts from untreated ones. Four analysed Magdalenian artefacts were most likely not to have been heat-treated due to the absence of other magnetic phases than magnetite. One further sample was probably burned; heat-treatment of the last artefact is ambiguous. The possible absence of heat-treatment in Moravian caves and in the Magdalenian in general may be due to the absence of pressure flaking in this culture.

The unique Solutrean laurel-leaf points of Volgu: heat-treated or not?

Abstract

Pressure flaking to serrate bifacial points for the hunt during the MIS5 at Sibudu Cave (South Africa).

Projectile technology is considered to appear early in the southern African Middle Stone Age (MSA) and the rich and high resolution MSA sequence of Sibudu Cave in KwaZulu-Natal has provided many new insights about the use and hafting of various projectile forms. We present the results of a functional and technological analysis on a series of unpublished serrated bifacial points recently recovered from the basal deposits of Sibudu Cave. These serrated tools, which only find equivalents in the neighbouring site of Umhlatuzana, precede the Still Bay techno-complex and are older than 77 ka BP. Independent residue and use-wear analyses were performed in a phased procedure involving two separate analysts, which allowed the engagement between two separate lines of functional evidence. Thanks to the excellent preservation at Sibudu Cave, a wide range of animal, plant and mineral residues were observed in direct relation with diagnostic wear patterns. The combination of technological, wear and residue evidence allowed us to confirm that the serration was manufactured with bone compressors and that the serrated points were mounted with a composite adhesive as the tips of projectiles used in hunting activities. The suite of technological and functional data pushes back the evidence for the use of pressure flaking during the MSA and highlights the diversity of the technical innovations adopted by southern African MSA populations. We suggest the serrated points from the stratigraphic units Adam to Darya of Sibudu illustrate one important technological adaptation of the southern African MSA and provide another example of the variability of MSA bifacial technologies.

Composition, Processing and Properties of Composite Ceramic Sickle Blades from Mesopotamia

ABSTRACTCeramic tools were made in lowland Mesopotamia from about 4500 to 2750 B.C.E. At first hammers, adzes, axes and sickles were made. By about 3300-3100 B.C.E., only sickles were made. We reverse engineered the technology to show that local, salty montmorillonite clay and quartz sand were formed into a composite blade and handle from a biconical coil and fired to 1120-1170°C based on analysis of refiring tests. At 1200°C the montmorillonite clay transforms to glass, so the firing range was right on the edge of slumping the ceramic into a useless mass. To prevent plastic deformation of the clay about 25-33 vol% of quartz sand was added. The extensive glassy matrix phase enabled the best blades to be resharpened by pressure flaking. The compositions, phase assemblage, firing temperature range, material limits on processing, and properties have been characterized for 15 sickle samples from Nippur using Xeroradiography, SEM-EDS, EPMA, and analysis of refiring tests. Strength and hardness tests and toughness calculations were conducted on replicate test tiles made using clay from Pit M at Nippur, Iraq, and sand.Based on finds of small groups of well-fused sickles that were overfired and melted together and our experiments that demonstrated the difficulty of controlling peak temperature range and firing time for the somewhat variable raw material, the sickles probably were fired in small groups, of perhaps 10-15, in small arched, tunnel kilns that achieved high temperatures by facing somewhat predictable oncoming wind flows that provided natural draft. No evidence of workshops has been located, but, based on the archaeological finds at Nippur and our analyses, we propose that sickle-making may have been practiced as a local, seasonal, popular technology with tools being made by farmers or part-time specialists who fired in small, temporary tunnel kilns in fields or near settlements during the dependable seasonal winds. This research investigated the sickles as a well-engineered, but risk-prone ceramic manufacture that fulfilled an important a societal need, agricultural success. The technological choices of craftsmen were narrowed by raw material constraints, risk-taking, practice and workmanship to achieve desired properties and performance characteristics.

Quelques observations d’ordre technologique et typologique sur les industries lithiques découvertes à Atmageaua Tătărască (Sokol, Bulgarie)

The site of Atmageaua Tătărască in Southern Dobrudja has a long occupation sequence, spanning from Boian A, Gumelnita A1, Gumelnița A2, to Gumelnița B. With a few exceptions, the archaeological patterns were not recorded during the excavations. The lithic industry includes 976 pieces, for most of them (72.84%) issued from the level III – Gumelnița A1. After analysing the material from level III, several conclusions arise. At least part of the knapping process was carried out locally, viz. for large and medium-sized blades. This paper puts forward the hypothesis of the presence of a workshop involving specialized knappers for level III. Blade production is predominant, and at least two reduction sequences were identified. Two types of percussion are observed : direct percussion with hard hammer (predominant) and indirect percussion ; conversely, pressure flaking technique is lacking. Tools amount to 36.56% of the assemblage and, supplemented by axes, up to 39.09%. Among the tools, the most numerous are burins (33.46%) and endscrapers (27.69%), followed by retouched blades (19.23%) and truncations (9.23%). Less represented tool groups are notches, sidescrapers, scaled pieces, retouched flakes, becs, as well as an arrow point. It is also worth mentioning composite tools (3.65%) and the reuse of old tools, which were re-shaped into new ones. The raw material is of high quality ; it is also fairly homogenous, giving preference to the local Ravno (93.54%) and Kriva Reka type of Ludogorie chert, yellow-brown and grey Upper Cretaceous flint (Moesian flint), but also a dark blue chert possibly issued fromthe middle Prut valley.

On Identifying Stone Tool Production Techniques: An Experimental and Statistical Assessment of Pressure Versus Soft Hammer Percussion Flake Form

Identifying stone tool production techniques in the archaeological record can inform on prehistoric economy, time budgets, shared cultural practices, and the spatiotemporal occurrence of technological innovations and adaptations. The pressure flaking technique is one such innovation that appears on every continent Homo sapiens colonized. Pressure flaking has long been associated with the ability of flintknappers to produce small, regularly shaped flakes that were used to maintain particular edge shapes and resharpen dull tool edges with minimal loss of raw material. Despite the importance of pressure flaking, a method for supporting the identification of pressure flakes in the archaeological record is lacking. Here, we present a stone tool replication experiment that statistically compares flakes derived from bifacial pressure flaking and soft hammer percussion flaking. Our analyses show that pressure flakes are on average lighter, shorter, narrower, and thicker than soft hammer percussion flakes. Discriminant analyses indicate that pressure flakes can be correctly classified at a rate of 70 percent in a mixed sample. Furthermore, our findings validate the assumption that pressure flakes are less variable in form compared to soft hammer percussion flakes. Based on our results, we suggest quantitatively reevaluating the presence of pressure flaking in the global archaeological record.

On Identifying Stone Tool Production Techniques: An Experimental and Statistical Assessment of Pressure Versus Soft Hammer Percussion Flake Form

Identifying stone tool production techniques in the archaeological record can inform on prehistoric economy, time budgets, shared cultural practices, and the spatiotemporal occurrence of technological innovations and adaptations. The pressure flaking technique is one such innovation that appears on every continent Homo sapiens colonized. Pressure flaking has long been associated with the ability of flintknappers to produce small, regularly shaped flakes that were used to maintain particular edge shapes and resharpen dull tool edges with minimal loss of raw material. Despite the importance of pressure flaking, a method for supporting the identification of pressure flakes in the archaeological record is lacking. Here, we present a stone tool replication experiment that statistically compares flakes derived from bifacial pressure flaking and soft hammer percussion flaking. Our analyses show that pressure flakes are on average lighter, shorter, narrower, and thicker than soft hammer percussion flakes. Discriminant analyses indicate that pressure flakes can be correctly classified at a rate of 70 percent in a mixed sample. Furthermore, our findings validate the assumption that pressure flakes are less variable in form compared to soft hammer percussion flakes. Based on our results, we suggest quantitatively reevaluating the presence of pressure flaking in the global archaeological record.

42,000-year-old worked and pigment-stained Nautilus shell from Jerimalai (Timor-Leste): Evidence for an early coastal adaptation in ISEA

In this paper, we describe worked and pigment-stained Nautilus shell artefacts recovered from Jerimalai, Timor-Leste. Two of these artefacts come from contexts dating to between 38,000 and 42,000 cal. BP (calibrated years before present), and exhibit manufacturing traces (drilling, pressure flaking, grinding), as well as red colourant staining. Through describing more complete Nautilus shell ornaments from younger levels from this same site (>15,900, 9500, and 5000 cal. BP), we demonstrate that those dating to the initial occupation period of Jerimalai are of anthropogenic origin. The identification of such early shell working examples of pelagic shell in Island Southeast Asia not only adds to our growing understanding of the importance of marine resources to the earliest modern human communities in this region, but also indicates that a remarkably enduring shell working tradition was enacted in this area of the globe. Additionally, these artefacts provide the first material culture evidence that the inhabitants of Jerimalai were not only exploiting coastal resources for their nutritional requirements, but also incorporating these materials into their social technologies, and by extension, their social systems. In other words, we argue that the people of Jerimalai were already practicing a developed coastal adaptation by at least 42,000 cal. BP.

Emergence of a microlithic complex in the Transbaikal Region of southern Siberia

Upper Paleolithic stone artifact microlithization embodied a change in tool design and production that noticeably impacted northeast Asian prehistory. Here we trace the process of microlithization in the Transbaikal Region of southern Siberia using core reduction event-trees and morphometric analysis of cores and their by-products. Microtechnology emerges in the Transbaikal in the Middle Upper Paleolithic just prior to the Last Glacial Maximum (LGM) in the form of highly variable microcores with small flakes and blades, and possibly sporadic pressure flaking and slotted tools. This variability indicates an experimental period in microlithic technology. After a 2000-year gap in the occupational record, a highly standardized microblade technological complex consisting of wedge-shaped microblade cores, pressure flaking, microblades, and slotted osseous tools appears in the Transbaikal as a fully adopted system. This evidence suggests that microtechnologies developed within the Transbaikal just prior to and during the LGM, underwent refinement outside of the region for roughly 2000 years, then was brought into the region during the LGM with flintknappers as a fully adopted system.

La anisotropía y el clivaje del cuarzo automorfo y sus posibles efectos sobre la talla: Una revisión bibliográfica [Anisotropy and cleavage of automorphic quartz and their potential effects on the knapping: A literature review

En los ultimos treinta anos, los arqueologos han comenzado a superar su tradicional desinteres por las industrias liticas realizadas en cuarzo, con un numero creciente de trabajos centrados en esta materia prima. Sin embargo, la mayor parte de estas aproximaciones se han centrado fundamental o exclusivamente en el cuarzo xenomorfo o “cuarzo de filon”. En cambio, la variedad automorfa de esta materia prima – tradicionalmente conocida como “cristal de roca” o “cuarzo hialino” – ha recibido una atencion comparativamente menor. En este articulo se describe sucintamente el estado de la investigacion sobre dos de las caracteristicas basicas del cuarzo automorfo: la anisotropia y el clivaje, con el objetivo de ofrecer, a aquellos investigadores que traten frecuentemente con este material, una base a partir de la cual poder aumentar su comprension sobre el comportamiento mecanico del cristal de roca. El cuarzo automorfo presenta caracteristicas o comportamientos especificos durante la talla, derivados no solo de la peculiar morfologia y tamano de sus soportes – monocristales de habito prismatico, generalmente de dimensiones reducidas – sino tambien de su naturaleza anisotropa (caracteristica por la cual ciertas propiedades fisicas de un material tienden a variar en funcion de la direccion en la que se midan) y quizas por la existencia de planos de clivaje (debilidades en la estructura del material por las que este tiende a partirse o separarse con mayor facilidad). En este sentido, las investigaciones llevadas a cabo tanto por arqueologos como – sobre todo – por geologos, mineralogos y cristalografos coinciden en senalar un desigual comportamiento mecanico de los cristales de cuarzo en funcion de la direccion en la que se propaguen las fuerzas a las que estos son sometidos. Asi, las fuerzas mecanicas (incluidas las generadas por percusion o presion durante la talla litica) tienden a progresar mas facilmente en aquellas direcciones oblicuas al eje longitudinal del prisma, mientras que su avance es comparativamente mas dificultoso cuando se produce en paralelo a dicho eje mayor. En cuanto a los planos de clivaje, su presencia en el cuarzo ha sido objeto de debate durante mas de un siglo, sin que los especialistas hayan podido lograr un consenso. La mayoria de los investigadores coinciden, sin embargo, en aceptar la existencia de algun tipo de control cristalografico de las fracturas en esta materia prima, refiriendose frecuentemente a un clivaje “imperfecto” o de “baja energia”.El impacto que dichas caracteristicas fisicas tendrian sobre la talla del cuarzo automorfo estan aun lejos de ser conocidas en detalle. Durante la ultima decada del siglo pasado, se instalo entre los especialistas una cierta vision de la anisotropia como un elemento limitador de la talla del cristal de roca, quizas un factor detras de su uso aparentemente residual a lo largo de la Prehistoria. Sin embargo, un vistazo al registro arqueologico contradice esa vision de escasez, con conjuntos en cuarzo automorfo repartidos por yacimientos de todo el mundo y con este material llegando a alcanzar un importante peso porcentual en contextos del Paleolitico Superior o Epipaleolitico. Ademas, en no pocas ocasiones, su explotacion ha implicado el uso de tecnicas relativamente complejas, como la percusion indirecta y la presion. Asi pues, parece evidente que ni la anisotropia ni la posible presencia de planos de clivaje habria sido un obstaculo insalvable para la explotacion del cuarzo automorfo. Sin embargo, tambien resulta cierto que una presencia mayoritaria, entre los conjuntos arqueologicos con presencia de cristal de roca, de estrategias de talla en las que se explotaron preferentemente aquellos planos en los que los estudios consultados indican que se produciria una menor resistencia del material a la progresion de las fracturas, sugiere que los talladores prehistoricos probablemente estaban al tanto de estas caracteristicas de la materia prima y que las usaron en su beneficio.