Fractures in Knapping

Are Tsirk

• Publisher: Archaeopress
• Year: 2014
• Print ISBN: 9781784910228
• eBook ISBN: 9781784910235
• Topic: Social Sciences
• Subtopic: Archaeology
• Index: Social Sciences

This book is for students and practitioners of not only knapping, lithic technology and archaeology, but also of fractography and fracture mechanics. At conferences on fractography of glasses and ceramics, the author has often been asked to demonstrate knapping as well as provide overviews of fractography learned from it. The first part of the book is intended to stimulate such interests further, in order to solicit contributions from a largely untapped pool of experts. Such contributions can advance significantly our understandings of knapping as well as fractography. In Part II of the book, fracture markings as the tools of fractography are introduced, with their formation, meaning and utility explained. Observations on the presence or absence of the markings in knapping are considered in Part III, along with a number of interpretations of fracture features. The basic principles and concepts of fracture mechanics and fractography apply to fractures produced in any cultural context. This volume therefore addresses most questions on fracture in a generic sense, independent of cultural contexts. In general, understanding of fractures provides a sounder basis for lithic analysis, and use of more recent scientific tools opens new avenues for lithic studies.

Table of contents

• Book cover
• List of Tables
• Copyright page
• Contents
• List of Figures and Tables
• Preface
• 1. Knapping Past and Present
• 2. Knapping Tools and Techniques
• 3. Raw Materials
• 4. An Overview
• 5. Hackles and Hackle Scars
• 6. Ripples
• 7. Mirror, Mist, Hackle, Branching
• 8. Miscellaneous Markings
• 9. Introduction
• 10. Flake Initiations, Proximal and Surface Features
• 11. Crack Paths and Flake Profile Features
• 12. Forces in Knapping
• 13. Breakage of Blades, Flakes and Bifaces
• Concluding Remarks
• Glossary
• References
• Index
• Fig. 1.2 A Solutrean laurel leaf from Volgu, France. The cast is 27.4 cm long and about 7 mm thick. (The photo is of a cast from the Museum of Man in Paris.)
• Fig. 1.3 A Paleoindian Clovis Point from Blackwater No.1 Site. 10.6 cm long. The arrow indicates a fracture marking known as a split ridge (Chapter 8), seen poorly. (Photo is of Bostrom’s plastic cast by Kristian Mets.)
• Fig. 1.4 Replica of an Egyptian Predynastic Gerzian knife. Flint, 25.2 cm long.(Kelterborn 1984. Reproduced with permission)
• Fig.1.5 Type IV-E Danish dagger. Errett Callahan’s replica of the famous Hindsgavl Dagger. Flint, 29.3 cm long. (Callahan 1999, reproduced with permission)
• Fig. 1.6 Type IC Danish dagger. Replica by Greg Nunn. An excellent example of edge-to-edge flaking. It broke during final retouch. Flint, ca 26 cm long. (Nunn 2006, reproduced with permission.)
• Fig. 1.7 Replicas of Neolithic square section axes of Denmark by Thorbjorn Petersen (Courtesy of Errett Callahan. Photo by Jack Cresson).
• Fig. 1.8 An exhausted blade core on the gunflint knappers work floor at Brandon.
• Fig. 1.9 Threshing sledges in Turkey. The one at the right, as well as the partly seen sloping one at the left, has two wide blanks. The lower two photos show the details of the flint blade inserts. These were in a “coffee shop” in the tourist section of
• Fig. 1.10 Knapped blocks at Eben-Emaël for porcelain industry. Squared blocks for end of the mill. (Callahan 1985. Reproduced with permission.)
• Table 3.1 Major Constituents in Obsidians
• Table 3.3 Constants for Thermal Effects
• Table 3.4 Examples of Fracture Toughness
• Fig. 3.1 Callahan’s proposed lithic grade scale (Callahan 1979, reproduced with permission)
• Fig. 3.2a Workability vs. K1c
• Fig. 3.2b Fracture Toughness vs. Lithic Grade
• Fig. 3.3 Potlid fractures: At the bottom of the center column is a potlid fracture on which a secondary one (shown above it) occurred at its inner surface. A potlid fracture with the associated potlid is shown in the right column.
• Fig. 3.4 A frost pitted nodule of Cobden chert.
• Fig. 3.5 Sinuous fracture of a chert biface due to cooling too fast. Burlington chert from Crescent Quarry.
• Fig. 3.6 A modern Normanskill chert quarry in Greene County, New York. The chert and the parent shale are used in contemporary construction. The scale of the operation is seen by the construction equipment in the background. The nodules and boulders seen
• Fig. 3.7 Use of flint for houses in Brandon, England. The Bell on the top left, presently an inn, has untrimmed flint nodules in the wall. The brick house on the right uses trimmed flint as decoration in the brickwork. It used to belong to the gunflint kn
• Table 4.1 Fracture Markings Terminology
• Table 4.2 Occurrence of Fracture Markings
• Table 4.3 Utility of Fract ure Markings
• Table 4.4 Clues from Fracture Markings
• Table 4.5 A Catalogue of Fracture Markings
• Fig. 5.1 Tails (as at A and B) and twist hackles as persistent tails (black arrow) in obsidian. The mist and hackle at the right (white arrow) is at the lip of a biface thinning flake. The gull wings indicate a very high fracture velocity. At B, the appro
• Fig. 5.2 Formation of twist hackles
• Fig. 5.3 Twist hackles at the edge of an obsidian flake. A number of smaller ones are seen to merge into a larger one, as at the arrow. Fracture direction is downward to the right.
• Fig. 5.4 Twist hackles at and near the edge of a biface thinning flake of a fine variety of Normanskill chert. The general fracture direction for the flake was downward.
• Fig. 5.5 Twist hackles and incipient twist hackles in a coarse variety of Normanskill chert. The characteristics of these markings are influenced by their angle with the general fracture direction (downward here) for the flake, as well as the size and nat
• Fig. 5.6 Twist hackles (arrow) and incipient twist hackles (especially in b) in Esopus chert.
• Fig. 5.7 Tails in obsidian often persist as twist hackle. The “flip-flop” by the arrow is due to the lateral breakthrough to o e and then the other side. The fracture direction was downward.
• Fig. 5.8 Tails at irregular inclusions in obsidian, formed by the fracture passing around and through the inclusion.
• Fig. 5.9 Parabolic double tails, formed as the fracture passes through the inclusion at its head, onto a different plane. Note the third tail in (c). Obsidian. Fracture direction downward.
• ig. 5.10 Parabolic double tails and many mist lines on the surface of a flake. Glass Buttes obsidian. Fracture direction downward. (Photo by V.D. Fréchette; from Tsirk 1996)
• Fig. 5.11 Parabolic double tails in a mist region. The fracture in the Jemez Mountains obsidian was caused by a forest fire at an archaeological site (Steffen 2005).
• Fig.5.12 Convergent tails with trailing mist line. Obsidian. Fracture direction downward.
• Fig. 5.13 Hackle scars at the edge of an obsidian flake. On the left portions of the figure, the fracture direction was downwa d.
• Fig. 5.14 An overshot hackle flake and its scar on an obsidian flake.
• Fig. 6.1 Stress changes associated with ripple formation
• Fig. 6.2 Ripple profiles and associated changes in shear stress.
• Fig. 6.3 Gull wings at numerous inclusions on a flake. Wallner wakes are barely seen at the arrows. Glass Buttes obsidian. Fracture direction downward. Width of field 1.8 mm. (From Tsirk 1988)
• (From Tsirk 1988)
• Fig. 6.5 Formation of gull wings
• Fig. 6.6 “Knappers’ Speedometer”
• Table 6.1 Errors (%) in VF/VS due to rotation of fracture plane
• Fig. 6.7 Wallner wake formation. (From Tsirk 1988)
• Fig. 6.8 An obsidian flake detached by percussion with ultrasonic modulation at 175 kHz. Fracture direction downward. (Courtesy M.G. Schinker for the modulation)
• Fig. 6.9 Sonic modulation (at 183 Hz) used on an obsidian pressure flaker. The fracture is propagating upwards at about 2 to cm/s. The dry parts (as at arrows) are lagging behind the leading wetted parts. The image width is ~2.8 mm.
• Fig. 7.1 Breaking stresses and mirror radii
• Fig.7.2 Mist (dashed arrow) and hackle (solid arrow) on an accidental break of a biface. The tensile face of the biface is a the right. Mist lines and narrow, parabolic doube tails are seen in the lower part of the mist region. Glass Buttes obsidian. Fra
• Fig. 7.3 Fracture surface of an accidental break from an internal flaw. Mist (dashed arrow in a) and hackle (solid arrow) are clearly seen in the obsidian.
• Fig. 7.4 A mist-hackle configuration (arrow) in a mist region in obsidian. Fracture direction is downward.
• Fig. 7.5 Mist line in obsidian Fracture direction downward.
• Fig. 7.6 Mist and hackle patterns. Mist lines in lieu of tails and twist hackles are manifested close to the general mist regions. Mexican obsidian. The fracture origin was near the top. The downward fracture direction is indicated by the mist lines.
• Fig. 8.1 Material interface ridges (solid arrow) and material transition ridges (dashed arrow) in obsidian.
• Fig. 8.2 Formation of a material interface ridge.
• Fig. 8.3 Split marks on a flake. Split step (dashed arrow) and split ridge (solid arrow) are seen.
• Fig. 8.4 Ruffles on the inner surface of an obsidian flake due to geometrical irregularities on outer surface. (From Tsirk 2012)
• Fig. 8.5 Variation of fracture velocity VF with stress intensity factor KI for dry, moist and wet environments for a glass
• Table 8.1 Basic Types of LIFMs (by Appearance)
• Fig. 8.6 The basic LIFM type called an escarpment scarp (arrow) on an obsidian pressure flake with the platform wetted with water. Fracture direction upward.
• Fig. 8.8 The basic LIFM type called linear band features (arrows). Obsidian pressure flake. Platform wetted with water. Fracture direction upward.
• Fig. 8.7 The basic LIFM type called a liquid-induced hackle (arrow). The platform was wetted with saliva for the obsidian pressure flake. Fracture direction upward.
• Fig. 8.9 The basic LIFM type called a cavitation scarp (arrow) on an obsidian pressure flake. Platform wetted with water. Fracture direction upward to right. (Adapted from Tsirk 2001.)
• Fig. 8.10 Two unusual encounter-depletion scarps. Obsidian, wetted with saliva. Fracturing upward. The upstream part of each scarp is an encounter scarp (arrow).
• Fig. 8.11 Sierra scarps in a soda-lime glass plate broken accidentally in a sink with liquid. Fracture direction is up to the ight. The upstream shoulders are encounter scarps, partly with escarpments (arrow) and partly with hackle scarps (dashed arrow).
• Table 8.2 Liquid-Induced Fracture Markings (LIFMs)
• Fig. 8.13 Miscellaneous scarps. Most prominent are the encounter-depletion scarps manifested in the form of fingerlets. Obsidian, wetted with saliva. Fracture direction upward.
• Fig. 8.12 An encounter scarp (arrow) manifested as a hackle scarp. Obsidian, wetted with water. Fracture direction upward.
• Fig. 8.14 Depletion scarps manifested as irregular fingerlets. Obsidian, wetted with blood. Such irregular fingerlets were never seen with water or saliva. Fracture direction upward to the right (Adapted from Tsirk 2001.)
• Fig. 8.15 Occurrence of scarps with distance from the fracture origin on pressure flakes of obsidian.
• Fig. 8.16 The very many inclusions of variable sizes in this pressure flake of industrial waste glass rendered the LIFMs (arrow) particularly conspicuous. Water used for wetting. General fracture direction upward.
• Fig. 8.17 The very many inclusions of variable sizes in the industrial waste glass led consistently to manifestation of very u usual and conspicuous LIFMs over the whole surface. Water used for wetting. General fracture direction upward.
• Fig. 8.18 Sonic modulation at 183 Hz was used for this obsidian pressure flake wetted with water. The encounter scarp (arrow) is formed when water becomes available from the right side. From the configurations of these Wallner lines, it is seen that water
• Table 10.1 Flake Initiations
• Fig. 10.1 Hertzian cone fracture.
• Fig. 10.2 Force vs. time for several impact velocities and sphere radius R = 5.1 cm..
• Table 10.2 Hertzian Cone Fractures and Hertzian Flake Initiations: Some Differences
• Fig. 10.3 Flake initiation by wedging in Normanskill chert: Solid arrow in both cases indicates a split cone or other contact eature. In contrast to the pronounced ripples in (a), the ripples in the more confined flat region in (b) (dashed arrow) are sub
• Fig. 10.4 Flakes with Hertzian initiation in Normanskill chert: (a) A cone-like feature with ripples. A ring crack is presen on the platform. Proximal width is 5.7 cm. (b) There are the proximal ripples but no cone-like feature and no ring crack. The He
• Fig. 10.5 Flake with Hertzian initiation. The cone-like feature has pronounced “step ripples”. Flake is 6.4 cm long at mid-sec ion. Normanskill chert.
• Fig. 10.6 Combined wedging-Hertzian initiations. The solid arrow indicates a partial cone-like or other Hertzian feature. The dashed arrow points to the “split” part of this feature. Nearly flat regions with ripples resembling circles are manifested in bo
• Fig. 10.8 A wing flake can drastically alter the edge angle for subsequent flaking, as seen in (b). A flake scar (2.6 cm wide) and wing flake scars are seen in (a). These are for the wider face of a square section axe.
• Fig. 10.7 A flake with a wing flake that was detached to the left side. Solid arrow shows the location of the Hertzian flake i itiation; dashed arrow, the twist hackle from which the wing flake originated. Moose antler punch used. Texas flint.
• Fig. 10.9 Flake initiation by unzipping. The arrow in (a) corresponds to the arrow at C in (b). The core platform was struck a number of times with a very hard hammerstone, roughly along the line of the prospective flake edge. The biggest Hertzian contact
• Fig. 10.10 Grinding over pecking on a platform of an Aztec blade from Otumba site in Mexico. The enlarged view in (b) is of the lower left part of (a). Pachuca obsidian.
• Fig. 10.11 Schematic outlines for cross-sections of a square section axe. For flake removal from the short face AB, it is adva tageous or even necessary to apply the force in the direction shown in (a). If the force is applied as in (b), the flake will te
• Fig. 10.12 Mist and hackle at the lip by the right edge of an obsidian biface thinning flake with bending initiation.
• Fig. 10.13 Proximal region of the same flake (adjacent to its platform) produced by direct percussion, having a bending initiation. A mist-hackle region adjacent to the edge is conspicuous, especially in (a). These regions characteristically occur when th
• Fig. 10.14 A hackle scar on a bulb, with the associated overshot hackle flake.
• Fig. 10.15 Variations of flake thickness in transverse direction affecting the fracture front and ripple configuration. In (b), it is partly concave in the downstream direction. (Adapted from Tsirk 1981.)
• Fig. 10.16 These ripple configurations relate to the variations in flake thickness in the transverse direction. (a) and (b) are obsidian. (c) is Normanskill chert. (a and b adapted from Tsirk 2012: Fig 7)
• Fig. 10.17 Material interface markings: Material interface ripple in (a) and material interface ridge in (b).
• Fig. 10.18 Split marks: Split step (solid arrow) and split ridge (dashed arrow). Esopus chert.
• Fig. 11.1 Popout and related fractures (schematic): (a) Popout fracture; (b) Stepout fracture; (c) Compression lip; (d) Compression wedge. (Adapted from Tsirk 2010b)
• Fig. 11.2 Nominal stress trajectories for bending of an uncracked (a) and partly cracked (b) specimen (Adapted from Tsirk 2010b).
• Fig. 11.3 Effect of shear on the direction of the compression lip: (a) cantilever beam with shear; (b) direction of the comp ession lip with the shear shown; (c) effect of the shear stress at an element just ahead of the crack tip. (Adapted from Tsirk 201
• Fig. 11.4 Regular popout fractures with and without a roll-in from a hackle scar. (Adapted from Tsirk 2010b)
• Fig. 11.5 Formation of a stepout fracture: (a) initial stepout phase with crack extending outward (case with no roll-in); (b) forces causing the stress at B by the unbroken ligament, (c) a completed stepout fracture. (Adapted from Tsirk 2010b)
• Fig. 11.6 Schematic profiles and fracture directions for popout and stepout fractures observed. (Adapted from Tsirk 2010b)
• Fig. 11.7 Incipient, quasi-stepout and quasi-popout fractures: The kinked profile of the primary fracture in (a) resembles a stepout fracture. The primary fracture profile in (b) has some resemblance to a popout fracture. With the part-through transverse
• Fig. 11.8 Partial profiles of obsidian blades with dorsal concavities for (a) popout fractures and (b) stepout fractures. (Adapted from Tsirk 2010b)
• Fig. 11.9 Regular but unusual popout fractures from percussion, all initiating from a single hackle scar in obsidian: (a) a popout fracture on a very thick flake; (b) a very long (74 mm) popout; (c) a thick flake with a massive popout; (d) a double-sided
• Fig. 11.10 Reverse (a and c) and compound popouts. (c) shows a reverse popout and stepout combination. All are obsidian, by direct percussion. (Adapted from Tsirk 2010b)
• Fig. 11.11 Double popouts. Note the compression wedge from which the regular and reverse popouts initiate. The dashed arrows i dicate the fracture direction. (Adapted from Tsirk 2010b)
• Fig. 11.12 Formation of popout fractures. (Adapted from Tsirk 2010b)
• Fig. 11.13 Popout fracture on an obsidian biface thinning flake (Max. width ~8cm) After a study of many popouts and other fracture specimens, it became apparent that intrusive hackle flakes (with hinge terminations) gradually ”evolve” into popout fracture
• Fig. 11.14 Comparison of intrusive hackle scars (a and b) with single-sided popout fractures (c to f) from direct (a,b,c) and indirect (d,f) percussion. (d) is Normanskill chert, others are Glass Buttes obsidian. (Adapted from Tsirk 2010b)
• Fig. 11.15 Flake terminations
• Fig. 12.1 Wedge loaded at its tip: (a) A force applied parallel to its median plane; (b) A force applied normal to its media plane; (c) Moment applied.
• Fig. 12.2 Wedge with a force applied in an arbitrary direction at distance e from its tip.
• Table 12.1 Normalized Force Variations with Wedge Angle
• Table 12.2 Force Variations with Distance from Edge (r/e)
• Table 12.3 Comparisons for Contact and Non-Contact Flake Initiations
• Fig. 12.3 A two-dimensional model for analysis of blade detachment forces subsequent to the initial phase.
• Fig. 12.4 Variation of forces with lengths of the detached part of the flake.
• Table 12.4 Properties of Some Woods
• Table 13.1 Dimensions (mm) of flakes with popout fractures
• Table 13.2 Nondimensional popout characteristics
• Fig. 13.1 Broken bifaces from the Caradoc Site, from the late Paleo-Indian ritual artifact deposit. Bayport chert. (From Fig. 2.8 in Ellis and Deller 2002, with permission)
• Table 13.3 Biface breakages considered
• Fig. 13.2 A Normanskill chert biface broken accidentally during manufacture. It is surprising that the flake (top) is unbroke . It started out as a thinning flake from the base (See the sketch). Then a crack from the bending break of the biface extended u
• Fig. 13.3 Overshot (white arrow) flakes on a Clovis preform from Blackwater No.1. One of these was split, as barely seen by the split ridge (black arrow). (Photo of plastic cast by Kristian Mets)
• Fig. 13.4 Biface with a laterally overshot flake, ruined by the transverse biface break at the location of the overshot. Normanskill chert, direct percussion. Actual size.
• Fig. 13.5 Biface with a longitudinally overshot flake. Obsidian, direct percussion. Actual size.
• Fig. 13.6 Schematic illustration of an amputation from direct percussion (to the upper end in Sect. A-A). Tension is at the top surface (in Sect. B-B), as indicated by the mist-hackle and by the compression lip. The fracture direction is shown by the arro
• Fig. 13.7 Blade detachment with (a) single and (b) double curvature bending deformation. (Adapted from Tsirk 2009)
• Fig. 13.8 Stresses in a blade with triangular cross-section from a bending moment M.
• Fig. 13.9 Geometrical properties of triangular, trapezoidal and rectangular sections
• Fig. 13.10 Examples of fracture fronts (dashed lines) and fracture directions normal to them. Obsidian. Fracture direction downward. Flake in (b) 9.7 cm long and 2.7 cm wide. ((a) adapted from Tsirk 2012)
• Table 13.4 Lateral Wedges and Branching Cracks on Biface Tensile Surface
• Table 13.5 Observation of Mist, Hackle, Mist Lines and Parabolic Double Tails on Biface Breakages (No. & [% of Bifaces])
• Fig. 13.11 Mist and hackle at a transverse biface break from bending in direct percussion. Normanskill chert of medium grade. (a) More mist is seen at the upper part, closest to the tensile face. (b) is to the right of (a). Mist (left) and (velocity) hack
• Fig. 13.12 Mist and hackle (arrows) on a section of a prehistoric flint blade from the 9th millennium B.C. In addition to the mist-hackle by the tensile face at the top, an intrusive mist pattern is also manifested at the interior (dashed arrow). An unusu
• Fig. 13.13 Mist and hackle at a transverse biface break from bending. Normanskill chert of medium grade. (a) More mist is see at the upper part, closest to the tensile face. (b) is to the right of (a), and (c) is to the right of (b). Hackle seen as the m
• Fig. 13.15 Mist patterns at the downstream faces of the slices seen in Fig. 13.16
• Fig. 13.14 Some types of mist patterns
• Fig. 13.16 Multiple blade breaks with two slices. Obsidian.
• Fig. 13.18 A pair of lateral wedges on a Cobden Chert biface, broken accidentally during manufacture.
• Fig. 13.17 Bowtie from blade breakage. Heat treated Arkansas novaculite. Twice actual size.
• Table 13.6 Observed obsidian slices
• Fig. 13.19 Slice formation with loss of contact.
• Fig. 13.20 Slice in biface breakage. Direct percussion with antler billet while end supported on thigh, apparently too lightly. Glass Buttes Obsidian
• Fig. 13.21 Moment reduction vs. blade geometry when starting a crack from the outer face.