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Practical Applications of Dekton Artificial Rock for Experimental Archaeology and Traditional Lithic Technology

by Ray Harwood and Otis Crandell

1. Introduction

Currently many flint workers have trouble acquiring material in adequate quantities and sizes of suitable for knapping large pieces and large numbers of pieces, both for producing their wares as well as for practice purposes to gain competence. A milestone of modern knapping may be on the horizon though. The Cosentino Group, a commercial counter-top material producer, is now manufacturing a material known as Dekton that is now available in a large array of sizes and colors.

1.1. Background on modern knapping

"Knapping" is the process of chipping away material from high silica stones like "flint" in a carefully controlled manner with special tools to produce sharp projectile points or tools like those found in ancient archaeology sites. Only stones with very high silica content will provide the fracture predictability required to achieve the finest of works. A knapper is one who forms flint-like stone implements by controlling the fracture of the material. These stoneworkers use material exhibiting a conchoidal fracture, often employing antler tools, wooden mallets, stone hammers, and other hard material tools. Flaking is a process of removing small pieces of material from a piece of stone by applying pressure, or percussion or a combination of the two usually in order to produce objects similar to prehistoric tools (Crabtree 1972).

Natural flint (as well as chert) is a form of quartz, itself a form of silicon dioxide. It occurs in layers and irregular nodules in the chalk and some other limestone. It is widely distributed around the world and was one of several materials used for Stone Age tools and weapons. Chemically, flint is complex. It is a fine mosaic of colloidal silica (opal) and crypto-crystalline silica (chalcedony). In the Northwest, ancient peoples utilized obsidian to a much greater degree than flint based on availability and workability.

Knapping experiments (lithic technology) comprises three factors – the lithic material (flint-like), the method, and the technique of knapping. The method is in the mind; the technique in the hands. There is nothing as potent as experiment for verifying ancient lithic manufacturing practices. Each lithic material requires a different tool kit and variants in striking platforms, therefore, it is important to replicate with similar lithic material. According to Callahan (1979:24) the most abused case is replicas being made with obsidian, and now glass, which were originally made from lithic material other than these. While material choice has no relevancy in lithic art or hobby knapping, it is crucial in proper replication procedures being used to obtain data.

In recent years the replication of prehistoric stone tools, spearheads and arrowheads has become a very popular pastime. The ability to fashion these chipped stone items is not only a rewarding hobby with many social opportunities, a lifesaving wilderness skill, popular art form and academic study tool for a brand experimental archaeologists known as “Lithic Technologists”. For experimental archaeologists, knapping experiments give insights into actions, thought process, motor skills, and material culture of ancient craftsmen. According to researcher Patterson (1987), “experimental flintknapping is one of the areas in archaeology where controlled experiments can be used to demonstrate cause/effect relationships that are statistically valid. This cannot generally be done the use of experimentally uncontrolled archaeological field data. While stone tools have been studied and experimentally made for a number of years, archaeologists are only beginning to realize the potential of experimental flintknapping for the development of analytical methods.”

As an art form, the image of flakes on stone has a strange attraction, a fascination perhaps held over from our Stone Age ancestors. In the United States, knappers frequently sell their work to collectors for large sums of money. Often, lapidary equipment and skills aid modern knappers to reduce the labor intensive nature of the craft and to conserve material. In modern knapping, raw material is often cut into slices or slabs to reduce materials wastage and optimize the amount of finished pieces that can be produced from a limited quantity of raw material.

1.2. Ideal characteristics of raw materials

Ideal lithic material for knapping, as documented by Crabtree (1967:8–9), are kinds of stone with the necessary properties of texture, elasticity, and flexibility. An even texture -homogeneity, relatively free of flaws, cracks, inclusions, cleavage planes, and grains in order to withstand the proper amount of shock and force necessary to detach a flake of a predetermined dimension. When the required amount of force is applied to a properly prepared platform, a cone is formed creating a conchoidal fracture and the subsequent reduction flake. Other criteria include luster, glassy, waxy, satiny, coarse, and flat. According to Callahan (1979), “one need not have the exact same lithic materials the original artifact in order to perform valid replication, so long as the replication is of the same lithic grade as the artifact original. Hence, I feel that insistences upon performing experiments in the exact same lithic media as the originals is over wrought.”

Information about lithic grade workability, originally developed by Callahan (1979:24), is presented in Table 1 and Figure 1 below.

Grade Example materials
0.5 opal, some cold asphalts, some very hard candies
1.0> obsidian, glass, ignimbrite, some opalites
1.5 coarse obsidian, tektite, pitchstone
2.0 fine-grained basalt
2.5 heated fine flints, less fine-grained basalts
3.0 finest flints
3.5 most lithic materials. finer cherts, chalcedonies, agates, jaspers, novaculites, silicified woods, quartzite (silicified sandstone), some flints, hornstone
4.0 silicified slate, andesite, coarser cherts, chalcedonies, agates, jaspers, novaculates, finer quartzites, siltstone, bloodstone, porcelain, siliceous limestone, quartz crystal, argillite
5.0 coarse quartzite, coarse rhyolites, felsites, common basalt
5.5 greenstone, coarser felsites

Note: Thermal alterations of materials may lower their grade by 0.5 to 1.0. Under optimum conditions, grade may be lowered by 1.5.

Figure 1. Graph of lithic grade and type.

1.3. Lack of raw material sources

Once the proper techniques are learned and muscle memory established, the limiting component on large dance blades or Duck River Swords was, and especially is, obtaining a large enough, crack free, piece of lithic material. Now with the unreasonably small weight limits (250 pounds per person, per year) put on obsidian collecting at the Glass Buttes, Oregon (traditionally, the main source of this material for modern knapping), it has become nearly impossible to obtain large specimens of raw material for big blades and artifact replication. According to Whittaker and Stafford (1999), the average modern knapper produces about 25 “artifacts” (objects) per month. Dr. Whitaker estimates that at the time of the study, there were as many as 5,000 active knappers, this would indicate numbers as high as 1.5 million flint chipped stone items being produces each year. When one sees the tremendous quantities of flint materials mined for knapping, it is no wonder the government has stepped in with heavy restrictions. Fort Hood, Texas, one of the more famous flint collecting areas, was closed down a few years ago for ethical violations, others sites have been mined out, and are now barren of usable material, some closed under the protective guard of the National Park Service or other conservation designations, as most are ancient flint procurement areas important to archaeology.

1.4. About Dekton

According to the large stone counter top manufacturer Cosentino Center (the North American branch of the Cosentino Group, which is headquartered in Cantoria, Spain), of late, they have a new flint-like product line made of a type of A type of pressed quartz material known as Dekton "ultra-compact surfaces" (personal communications with Cosentino representative (personal communications 2015). Dekton is manufactured in Almeria, Spain using exclusive Cosentino TSP technology (Technology of Sintered Particles) a manufacturing process that uses an accelerated artificial metamorphic process (also referred to as a sintering process on the Dekton website [http://www.dekton.com/usa/what-is-dekton/]), to approximate the high pressure and high temperature which occur in nature over thousands of years. With Dekton though, the manufacturing takes about 4 hours. The press applies pressure at 5600 pounds per square inch.

According to the Dekton technical manual, the raw materials are quarried from various locations (although their documentation does not specify the locations), and are completely inorganic, containing no resins or organic components. These components are milled. The particle sizes are not specified but might be partially inferred from petrographic analysis. Pigmentation is a separate process produced by adding materials to the other pre-established components. The technical manual indicates that one example of the chemical composition of Dekton is as follows: aluminum silicates, amorphous silica, crystalline silica, zircon and inorganic pigments. The content of crystalline silica (likely quartz) in all colors and formula will always be below 11% in weight. The Cosentino representative (personal communication 2015) described Dekton as being made from a blend of raw materials comprised of refined glass, enhanced porcelain and natural quartz pressed with heat to form Dekton.

Cosentino produces slabs with a surface area of approximately 3.2 meters (10.5 feet) by 1.44 meters (4.72 feet) and with thicknesses between 8 and 30 millimeters (0.315 and 1.18 inches). These thicknesses are ideal for preform slab knapping. With such large dimension slabs being produced, it seems likely that discarded end pieces would likely be idea for further cutting into preforms for a variety of knapped tools.

Figure 2. Cutting a discarded piece of a Dekton slab.

Figure 3. An example of a projectile point knapped from a slab of Dekton synthetic stone next to an unused slab of the same material.

2. Testing and Workability

2.1. Physical and practical testing

This material was subjected to several tests and analyses to determine its suitability for use as a flint substitute. The main analyses looked at ease of workability, quality for usage, and general characteristics. There are 10 colors and as many multicolor selections, all with very natural appearances. The samples tried were Ariane (white), Sirus (black), and Kadum (mottled browns).

Presented in a question and answer format, the testing included the following. Note that Tests 1-3 were considered to be subjective, while Tests 4-9 were considered objective (i.e., they can be measured to some degree).

1. How much pressure is needed to push off a flake?

Pressure flaking using the Waldorf table method one would get the expected resistance as from a George Town flint type material, it is harder than obsidian, a bit tougher than dacite. With an Ishi stick, sitting in a chair with the thigh providing the energy, the flakes release about like dacite, thick platforms require some muscle. Keep in mind we are focusing on a material to produce massive biface blades. It does work with pressure, but not as well as dozens of glass and porcelain types, or obsidian, flints and cherts.

2. How predictable are the flakes when pressure or percussion knapped?

As well as highly homogenous natural lithic material. There are no inclusions, dry spots, concrete pockets, bubbles, cracks and so on. It is clean and holds together for massive biface knapping. Samples are very thick, enough abundance for type IV Danish Daggers as knapped by Errett Callahan and Ed Mosher, massive Emory Coons or Ted Orcutt biface sub types including the Riddick movie blades, Harwood long blades, Cole Hurst and Mike Tylznski type ceremonial blades, Phil Love type one piece long swords, and so on. As far as size of material, there is nearly no limit.

3. How brittle is the edge of a blade?

Like obsidian, on very thin edges you can crush off particles with your fingernail, yet the flakes hold together as well as Wagner basalt.

4. How many times can a piece can be used to slice orgouge wood or to saw wood or bone before it dulls?

Multiple experiments sawing through branches of newly fallen Ponderosa pine were conducted. Traditionally knapped bifaces of various lithic materials were used in the experiments. The Dekton biface blade edge worked as well as the rest in the task set. The wood was still a bit green, which is customary in primitive skills wood working, the areas I sawed though were knot-free and had no hard healed spots. Of course, working softwood reacts differently than hardwood, and Ponderosa pine is fairly soft. Similarly, Elk bone is harder than deer bone. The obsidian dulled on soft wood in the under-500-strokes realm before requiring retouch sharpening, the flint, Dekton and novaculite continued to be effective for another two hundred strokes. In my technically uncontrolled experiments, novaculite tended to hold an edge the longest on soft wood. For bone I used a fairly dry, but killed this year, Elk femur bone. The stone order of performance was the same, and as expected, with the heavy bone the blade edges dulled in a few as 40 strokes for the obsidian and 65 strokes for the novaculite, with the Dekton and flint falling in the middle at about 55.

6. How long can it cut grass or cereal grain stalks before it dulls?

I conducted grain harvesting cycle experiments with blades of Dekton and after 1,500 swings into thick foliage the blade edge sharpness was unaffected.

7. How much force is needed to percussion flake and to pressure flake it?

Much like unheated flint. It has a Georgetown-like feel. Knapping with wood, antler, sand stone or copper precursors. Overall, the material knaps well.

8. Does it make a nice, even and predictable flake? How is the edge (e.g., smooth, rough, rippled, irregular, other)?

Although there is some light rippling, the tested Dekton samples were found to flake well with "bopper percussion bifacing", lever flaking - flat work, and pressure flaking. Compared to the Lithic Grade Scale, it would have a value of about 2.5, placing it well within the realm of the average knapper's pressure capability. The black is much like the Wagner basalt of Arizona and the brown, like a nice flint. Planned platforms always out perform more random percussion methods. Long traveling flakes can be had with preplanned platform and precise execution. Systematic biface reduction sequences outlined by Callahan (1979) were followed, where biface reduction was analyzed in terms of seven stages: obtaining the blank, initial edging, primary thinning, secondary thinning, shaping to preform, finishing, and reworking or rejuvenation. Diagnostics for the stages were based on the cross-sectional shape of the tool, its width-to-thickness ratio, and its flake scar pattern. Less detailed stage distinctions were proposed for the associated debitage: indicators of relatively early-stage work included cortex, simple dorsal scar morphology, remnants of ventral flake bulbs on dorsal surfaces, and single-faceted platforms.”

Figure 4. Blades produced from Dekton.

Depending on the knapping strategy employed, lithic flake morphology reacts on Dekton similar to knapping Wagner basalt, ignimbrite of to a lesser degree dacite. With pressure aided by a fulcrum lever device a somewhat diffused bulb is produced, with percussion, a much more pronounced bulb and accentuated hatchure lines, ripples and errailures. The flake morphology is far less pronounced that obsidian, again akin to Wagner basalt of “basidian”. With proper platform preparation, the predictability of flake detachment and flake termination is high. The material is very homogeneous and granulations are a miniscule factor in Decton flake travel. “Simply stated, it knaps like Wagner basalt.” It was possible to send flake scars to the medial section without extensive platform prep. The material will follow all the rules of fracture mechanics, given all the basic preparations and knapping systems are adhered to.

The surface of the flaked material has a somewhat waxy feel, like the best fine grained basalts or rougher obsidians, a bit like ignimbrite or the sawed surface of novaculite. The sawed surface is very slick to the touch, even dry. Scratched with the finger nail, it sounds like a medium porcelanite or flint. It is difficult to discern the texture of the material, as some of the flake ripples are miniscule and close together, but they are detectable – not as much as porcelain and almost on par with obsidian, somewhat less than Wagner.

9. Are there any different characteristics for the different colors?

Yes. Sirius (from the the Dekton by Cosentino “Solid” collection), is black and is near indistinguishable from Wagner black basalt in the bifaced form. It is similar to their Domoos black. It performs with percussion and lever methodologies and as well as expected in pressure flaking studies for its given place in the lithic grade scale. Kadium (from the Dekton by Cosentino “TECH” collection), is similar in color and appearance to some brown American jaspers and ignimbrites. It is slightly waxier in texture than the Sirius and it’s knapping performance is slightly better than the Sirius. The chalk white materials, Zenith and Ariane (both from the Dekton by Cosentino “Solid” collection) also flake well. It is extremely important to note that these listed above are the only highly percussion knappable of the test samples in this study. The Natural from the Dekton by Cosentino collection, for example, is extremely hard to knap in comparison – like a tough porcelain toilet tank or floor tile. Some of these are very attractive, but are very much harder to knap.

2.2. Petrographic investigation

When viewed in thin section under a petrographic microscope, various characteristics of this material become apparent. One of the first things noticeable is that very few crystals are visible in crossed polarisers view. (see Figure 5.) There are some quartz crystals visible though. These are the white shapes visible in the left column of images. By contrast, almost all natural knappable materials will contain large amounts of quartz (obsidian being a common exception). (See the numerous white and grey crystals in Figure 6.) Normally in single polariser view, there should be no quartz visible. The structures visible in single polariser view represent other components - likely ground and melted materials (including former quartz and porcelain). Melted materials (e.g., glass - melted quartz) are mainly opaque (black) in crossed polarisers view. This would make sense based on how the material and its production are described (i.e. melted). (For notes on descriptive terminology, see Crandell 2005, 2006.)

Flint and chert are usually almost pure quartz - microcrystalline varieties, in fact. They may also contain smaller amounts of other materials, particularly iron oxides, . Note, for example, the rhomboid shapes in Figure 6 c & d. These are dolomite crystals. Metamorphic and diagenetic rocks such as quartzite (including orthoquartzite) tend to have much larger quartz crystals as well as larger amounts of other materials

Another thing to notice is the quartz size. It's much bigger in the Dekton than in flint and chert, and the size is quite variable. In flint, the quartz (in fact, microquartz) is all small and relatively uniform in size. This uniformity in size is what makes for a predictable conchoidal fracture. The quartz is what gives the blades a resistant edge after much cutting, chopping, harvesting, or other activities.

Based on petrographic analysis of brown and white samples, it seems likely that the white Dekton would fracture more predictably since it has a smaller particle size (regardless of what that other material is) and its particle size seems to be more uniform. It does not seem that predictability is related to the color. Fracture predictability is probably due mostly to having been produced with a different combination of materials (or material sizes). Alternatively, the company might simply have not been consistent with the production methods and this particular batch of white turned out that way (note that in the microphotos of natural materials, the background is brownish or beige because of the light from the microscope. A different lighting was used for the Dekton samples. The color difference between the images is not relevant to this study).

Figure 5. Microphotos of Dekton samples. a & b. sample 1, white Dekton; c & d. sample 2, white Dekton; e & f. samples 3, brown Dekton; g & h. sample 4, brown Dekton. Left side, one polariser (1P). Right side, the same view with crossed polariser (+P).

Figure 6. Microphotos of various natural materials. a & b. flint (from chalk outcrops); c & d. chert (from limestone outcrops); e & f. fine grained siliceous sandstone (also known as orthoquartzite); g & h. coarse grained quartzous sandstone. Left side, one polariser (1P). Right side, the same view with crossed polariser (+P).

3. An evaluation of Dekton for knapping purposes

As noted in Table 2, below, Dekton is on par with heat treated flint for knapping quality but available in massive size slabs. It is an isotropic material (the higher the number, the better the quality) having the same properties in all directions. It is typical of amorphous substances and crystals of the isometric system. In an isotropic elastic medium, the velocities of propagation of elastic waves are independent of direction. Isotropic values indicate a homogeneous structure of nature or kind throughout. In selecting lithic material for replication, one of the major criteria is homogeneity. A homogeneous material can be worked with consistency because it has no planes of weakness or included material that would impair the conchoidal fracture process (Crabtree 1972).

Table 2. Comparison of commonly knapped materials
Material Lithic Grade Isotropic Value Common Size Common Sources glassy
Glass 1.0 5.0 mega man-made glassy
Obsidian 1.0 5.0 large outcrops, ledges glassy
Dekton 2.5 5.0 medium man-made waxy
Heated Flint 2.5 2.5 medium man-modified waxy
Flint 3.0 3.0 medium quarries dull
Agate 3.5 2.5 small outcrops glassy
Chert 3.5 2.5 medium veins dull
Jasper 3.5 2.5 small outcrops glassy
Quartzite 3.5 2.0 small concretions granular
Porcelain 4.0 5.0 medium man-made granular
Basalt 5.0 3.0 large outcrops, ledges granular

With this new product available, the lack of large pieces of flint-like stone will no longer be a limiting factor for researchers or production knappers. According to Mr. Emory Coons (personal communication 2015) of Bend Oregon, an expert in very large flint and obsidian blades, he still has some large lithic pieces left from years past, but admits obtaining large samples of materials is an issue for most knappers working big flint blades, swords, and daggers. This observation was also discussed with Mr. Grog Verbeck of Lake Tahoe, California, at Emory's retail booth at the 2015 Quartzite, Arizona, rock, gem and mineral show, where both of these knappers looked forward to the prospect of a readily available man-made flint-like resource. Mike Tylznski of Idaho, another knapper of giant stone blades, also looks forward to testing the new Dekton material, saying that, “being very wide long and thick, it will be very beneficial in the advancement of big blade knapping research. I am curious if thermal alteration will improve the quality.” (personal communication 2015).

4. Conclusions

In line with Callahan’s concepts of artifact replications prerequisites, as long as the same knapping procedures and tools are required to replicate the original artifact in its original material, Dekton appears to be a valid substitute for any experimentation in the 2.5–3.0 range of the lithic grade scale. Dekton's location on the scale would indicate correct tools for optimum reduction during experimental research such as antler billet (1.0–4.5+), soft hammerstone (1.5–3.5), wooden billet (0.5–5.5), and pressure flaker (0.5–3.5). Additionally, the ultra-flexural strength limits end shock and makes this material optimal for large blades such as giant ceremonial Deer Dance, Sweet Water, and Duck River types. The fact that the material is available in a nearly limitless size range concerning length and width and a running thickness of 3cm or 1¼ inch slabs, it is ideal for Danish Dagger work. In the end, the availability of Dekton no longer limits our acquisition of large stone to create large, expert (and eventually, master-level) bifacially flaked pieces for both art and experimental archaeological endeavors.

Ray Harwood (figflint@yahoo.com)

Otis Crandell (crandell@ufpr.br)

References Cited

Callahan, E. 1979, The basics of biface knapping in the eastern fluted point tradition: A manual for flintknappers and lithic analysts (1st ed.). Archaeology of Eastern North America Vol. 7(1). Eastern States Archeological Federation, Washington, Connecticut, 213 p.

Crabtree, D.E. 1967, Notes on Experiments in Flintknapping: 3: The Flintknapper's Raw Materials. Tebiwa, 10(1): 8-24.

Crabtree, D.E. 1972, An introduction to flintworking. Occasional papers of the Idaho State University Museum Vol. 28. Idaho State University Museum, Pocatello, 98 p.

Crandell, O.N. 2005, Macroscopic analysis and characterisation of chert for provenance purposes. Sargetia, Acta Musei Devensis, 33: 137-153.

Crandell, O.N. 2006, Macroscopic and microscopic analysis of chert; A proposal for standardisation of methodology and terminology. Bulitnul Cercurior Stiintifice Studentesti, 12: 7-30.

Patterson, L.W. 1987, The Importance of Experimental Flintknapping in Archaeology. In: Flintknaping: An Emic Perspective (Harwood, R.H., Atwood, J.E. & Bailey, R., Eds.), Harwood Archaeology, Palmdale: p. 4-5.

Whittaker, J.C. and Stafford, M. 1999, Replicas, fakes, and art: the twentieth century stone age and its effects on archaeology. American Antiquity, 64(2): 203-214.

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