Are the Pyramids of Egypt Built of Poured Concrete Blocks?

Transcription

1 Are the Pyramids of Egypt Built of Poured Concrete Blocks? Robert Louis Folk Department of Geological Sciences University of Texas at Austin Austin, Texas Donald Harvey Campbell Construction Technology Laboratories 5420 Old Orchard Rd. Skokie, Illinois ABSTRACT Since 1974 Joseph Davidovits, a French concrete chemist, has been proposing that the pyramids and temples of Old Kingdom Egypt were built of geopolymer "concrete" poured into molds, rather than quarried blocks of limestone. We use geological evidence and engineering principles to demonstrate the flaws in this daring hypothesis. Pyramid and temple blocks show sedimentary bedding, burrows, and optical and SEM-scale properties characteristic of normal microporous limestones, and they are cut by tectonic fractures. Block dimensions and shapes are not likely to be the product of pouring into wooden molds, and some blocks show quarrying marks. It is not easy to give a geological education to a brilliant and determined chemist. Keywords: Petrology - sedimentary; engineering and environmental geology; Egypt, pyramids, limestone, concrete, archeology. Introduction During Old Kingdom times (around 2700 B.C.), the Egyptians developed through alchemy a method of making artificial stone by pouring a mixture of natural geologic materials with water and lime into molds, and thus making synthetic pyramid and temple blocks as an early form of concrete or "geopolymer." Because the mix was poured by the bucketful in situ on the sides of pyramids and temples, all the problems of quarrying, transporting, and hoisting heavy blocks were avoided - technological problems that have baffled engineers and Egyptologists to this day, because during Old Kingdom times the Egyptians did not know about wheels, pulleys, or cranes. Pyramid and temple stones, therefore, illustrate an ancient and forgotten technology not equalled to this day. So runs the amazing theory of Dr. Joseph Davidovits, head of the Geopolymer Institute of the University of Compiegne, France, who is widely respected in the industrial world for his innovative contributions to concrete technology and chemistry, and who holds over 20 patents on the formation of novel cements for which he has invented the term, "geopolymer." Since 1974, Davidovits has been presenting his theory at meetings of concrete technologists, archeologists, and Egyptologists; the most thorough exposition is given in a book co-authored by Margie Morris (Davidovits and Morris, 1988). The theory has been presented in several other books and many abstracts in the concrete and archeological literature (for example, see Davidovits, 1987). The Davidovits-Morris book is beautifully written, with citations from hieroglyphic texts, Greek and Latin writings, and it presents novel chemical ideas. It is a fine accomplishment, a truly innovative work and its authors are to be congratulated. The book is very convincing to the scientifically inclined layman and won a medal from the American Library Association. The theory has been geewhizzically reviewed in the public press and popular magazines such as Omni (Starr, 1983) and was slated to be the subject of a special TV program by NOVA. However, Davidovits admits the book was never peerreviewed, and he plunged ahead with promoting his theory despite objections by many geologists and archeologists, Journal of Geological Education, 1992, v. 40, p. 12 most of whom thought the geopolymer hypothesis was too ridiculous to be taken seriously; the only published review to date is a scathing denunciation by Bianchi (1989) in the archeological press. Davidovits' fascinating theory is invalidated by one fatal flaw: his basic premise of a geopolymeric origin for the stones is completely erroneous (Folk and Campbell, 1990; Campbell and Folk, 1991). We feel it is the duty of professional geologists and other scientists to expose this egregiously absurd theory before it becomes part of entrenched pseudoscience like that of the Von-Daniken or Velikovskian cults. Poorly founded theories of wide popular appeal like this give all scientists a bad reputation and devalue valid scientific methodology. Our interest in the geopolymeric theory began in 1984, when Folk was asked by Davidovits and Morris to cooperate in the study of pyramid specimens. Later, Campbell (1988) reported to Davidovits the results of his investigation of a Khufu pyramid sample supplied by scientists at the British Museum in London. Campbell and I both thought the theory was ingenious and novel, a brilliant intellectual effort, and that it had a chance (albeit a small one) of being right; it was clearly worth more than a quick dismissal. When Marshall Payn of the Epigraphic Society and Explorers Club offered us the chance to go to Egypt in January, 1990, we eagerly accepted the opportunity to give the idea a fair scientific evaluation, and, together with Margie Morris, we spent several days at Giza (Khufu, Khafre and Menkaure Pyramids), at Saqqara (Djoser Pyramid complex) and at the Cairo Museum evaluating the geopolymer theory. Within the first minute at the Khufu (Cheops) pyramid, we knew that all other Egyptologists and geologists were correct and that the pyramids are built of real limestone blocks, not of concrete. We went on to inspect other pyramids and temples to give the geopolymer hypothesis a fair shake and to gather evidence for or against the natural geologic origin of the blocks. It was a challenge to come up with clear evidence that would be convincing to those who have no geologic background, particularly to a genius in chemistry who had held this hypothesis as an idee fixe for 15 years, had three books, and had invested much scientific capital in the concept. As of this writing (1991), we have not yet convinced either Davidovits or Morris that their idea is wrong, but we will present here the kind of evidence and reasoning geologists use, hoping to educate non-geologists about the properties of real rock as opposed to concrete. We ask the readers to evaluate the evidence and make their own decision as to which idea is correct. We had originally hoped to present our findings as a dialogue, in the form of (1) statements from the Davidovits-Morris book, (2) our geologic evaluation of these statements, and (3) a response from Davidovits. However, Davidovits has not answered any of the numerous scientific objections raised by our report and over a year has elapsed since we sent him our first observations. Morris has valiantly carried on the discussion in his place, but the creator of the radical theory has not yet seen fit to rise to its scientific defense. What are our credentials for this study? Folk has studied limestone petrography since 1946 and thinks he knows what real rocks look like; he has also been involved in geological

2 Figure 1. Small-scale lamination, ripple marks, and cross bedding in a block, pyramid of Khufu; pen is 14 cm long. archeology in Yugoslavian Macedonia, Israel, and Magna Graecia (Southern Italy). Campbell has both graduate degrees in sedimentary geology and for sixteen years has been a specialist in cement mineralogy and concrete technology (see Campbell, 1986) so he can identify concrete in the field and under the microscope, and he is also able to argue geologic matters with Folk. The authors believe that, if Davidovits had any understanding of basic geologic principles and understood the implications of the obvious geologic evidence displayed at Giza, he would have realized that his geopolymer theory has no basis in fact. The Davidovits Theory In brief, Davidovits' theory is that Egyptian workmen went to outcrops of relatively soft limestone, disaggregated it, and then mixed the crushed fragments (including fossils) with water, lime, and zeolite-forming materials such as kaolin, silt, and natron (sodium carbonate). The slurry was carried up by the bucketful and then poured into wooden molds placed on the pyramid sides. This synthetic limestone, bonded by geopolymeric (zeolite) cement, hardened quickly into resistant blocks that have lasted almost five millennia. The stability of pyramid stone has been repeatedly cited by Davidovits in connection with his quest for commercial applications of his own novel, certainly genuine, cement formulations, advertised as being based on ancient Egyptian technology. During the mid 1980s, Davidovits assisted scientists and engineers at Lone Star Industries in Houston, Texas, in formulating "Pyrament," a quick-setting, high-strength cement using a pyramid as the advertising logo. In the following sections, we contrast the evidence presented by J. Davidovits and M. Morris (JD), who favor the geopolymeric origin of the pyramid and temple blocks, with what we claim to be the geologic explanation for the same features (FC). At the outset, it is clear that two types of limestone blocks occur in the pyramids: (1) core stones, which form the great bulk of the edifice and (2) casing stones, which consist of fine homogeneous Eocene Tura limestone (or geopolymer if you wish). This limestone was used as the outermost layer of blocks to make a higher-quality covering and also formed the lining of chambers and passageways. Granite blocks were used as casing stone on the Menkaure pyramid, as lining of the "King's chamber" in Khufu, and as walls in the Valley Temple of Khafre. Layering in blocks. JD: Layering in temple and pyramid blocks consists of "lift lines" caused by interruptions in Journal of Geological E< Figure 2. Sedimentary layering in a block on Khufu pyramid; many large burrows occur below the pen, and there is a tectonic fracture filled with calcite (arrow). concrete pouring (such as overnight pauses) so that the succeeding layers have different textures or compositions. FC: There is no doubt that modern concrete structures show "lift lines." However, to any geologist it is obvious that the layering in the pyramid and temple blocks is sedimentary bedding of natural origin. Some of the pyramid blocks show small-scale lamination, cross bedding, and ripple marks, unquestionably not characteristic of poured concrete (Figures 1 and 2). Concrete "stratification" does not show the effects of low-viscosity, unidirectional currents. One of the most trenchant observations is that, in rows of temple or pyramid stones, adjacent blocks often show the same vertical sequence of textural variations and stratification brought out by differential weathering; for example, a recessed zone may appear near the middle of a row of blocks (Figures 3 and 4). JD: According to the geopolymer idea, the workmen used materials that varied in composition between pours, and that in a row of blocks they changed the composition in the same sequence for each block. FC: The real explanation is that the Egyptians quarried blocks from the same series of beds and placed them next to each other, retaining to a major extent the stratigraphic continuity in the construction. At Saqqara, Clarke and Engelbach (1930, figure 101; our Figure 5) photographed a row of temple blocks that appears to show large-scale dune cross bedding continuously across many blocks, with no apparent offset of beds between the blocks (we have not seen this temple ourselves). The Egyptians seem to have attacked the quarry face using some type of sawing procedure, cut the blocks with virtually no waste except for the minimal few-millimeter width of the saw cut, and placed them in the temple walls exactly in their original configuration. This amazing accomplishment certainly delivers a devastating blow to the geopolymer idea. In the Djoser Pyramid at Saqqara, the core blocks weather to a finely laminated appearance due to the presence of thin clay layers, certainly not a property of concrete. The rounded form of Saqqara core stones is the result of millennia of spheroidal weathering (Figure 6), and does not signify that they were made like molded bricks (JD, figure 37). At Khufu, some pyramid blocks are positioned with their bedding vertical (Figure 7), an impossibility for concrete "lift lines." Morris replies (personal communication) that these were probably replacement blocks, laid in much later by pharaohs who wanted to restore the pyramids to their original grandeur after they had been used as convenient quarries in cation, 1992, v. 40, p. 26

3 Figure 3. Valley Temple of Khafre. Note the sedimentary stratification within the blocks; the three blocks in the nearest portion of the wall each show a more resistant bottom layer and must have been placed in the same stratigraphic sequence of beds in the limestone quarry. Photo: Jennifer L. Folk. Figure 5. A copy of figure 101 from Clarke and Engelbach (1930); V Dynasty Temple walls in which faint cross beds appear to sweep continuously across all the blocks on this face; they must have been carefully sawn in outcrop and then laid into the wall in precisely their original stratigraphic relationships. Blocks adjoin each other with sloping sides and some L-shape re-entrants. Figure 4. Enormous blocks in the Valley Temple of Khafre; central block is about 2 meters thick. The stratification sequence in this block is the same as that in the block to its left. Note the L-shaped re-entrant in the block at lower right which is not likely to be found in a geopolymer block poured into a mold. Arrow points to tourist's head. Figure 6. Step-pyramid of Dzoser at Saqqara. Irregularity in sizes and shapes of blocks indicates that they are real quarried stones, not blocks molded like bricks. Rounding of blocks is caused by millennia of weathering producing spheroidal form. antiquity. It is in fact well known that the casing stones were stolen as a source of fine building stone for Cairo about 1,000 years ago, but the poorer-grade core stones were more likely left in place - and certainly not restored later. It is unfathomable that the supposed "repair stones" would have the same stratal layering as those on each side, and furthermore they would show the same degree of weathering as their "original" neighbors. Thus, we believe that the rare blocks that show vertical stratification are original Old Kingdom blocks now sitting as the masons placed them 4600 years ago. Spongy Zones At Khufu, the tops of nearly all pyramid blocks are spongy (Figures 7 and 8). JD attributes this to lighter, more easily weathered, material floating to the top of the geopolymer slurry as it was poured into molds. FC: Actually, these are zones of honeycomb weathering, common in desert outcrops of limestone (an Egyptian outcrop example is shown by Aigner, 1982, figure 3). This weathering often emphasizes a pattern of burrows (Figure 8). In fact, on bedding surfaces we have seen curving burrows about 1 cm wide and decimeters long. We believe the reason that the spongy layer is usually concentrated at the tops of the blocks is due to the ponding of rain water on the tops of the blocks as they are exposed on the face of the pyramid like a series of steps. In some temple blocks, the honeycomb weathering zone is in the middle of the block (Figure 9) because of the greater susceptibility of certain beds to that style of weathering, thus contradicting JD's notion that the low-density spongy-weathering material floated to the top of "pours." We saw one block on Khufu that was set with its bedding vertical; it shows a vertically trending spongy zone caused by

4 Figure 7. Pyramid of Khufu. In this block the bedding is vertical; the white pen is placed in a more weathered bed, and other spongy-weathering sedimentary layers also are vertical. However, crossing the top of the block is a horizontal spongy zone, the result of more intense honeycomb weathering at the top of the block. This "Khufu Stone" clearly belies JD's idea that sponginess is due to lighter geopolymer rising to the top of the block and proves a geologic origin for the "sponginess." Figure 8. Pyramid of Khufu. "Spongy Zone" at the top of the block is obviously due to differential weathering out of burrows that are mainly horizontally oriented. weathering out of burrows, and in addition at its top shows a horizontal spongy zone due to ponding of water (Figure 7). There is no conceivable way that a concrete pour could show two perpendicular spongy zones. Like the Rosetta stone, this "Khufu stone" gives the definitive answer to the problem, and this translates to a deafening NO! to the geopolymer hypothesis. Fossils JD holds that fossils (particularly nummulites) were mixed in with the geopolymer slurry and poured into molds. His presumed good "geologic evidence" (Davidovits and Morris, 1988, p. 89, 90, 106) is that in normal limestones the fossils should be oriented more or less horizontally, but in the pyramid blocks they have a jumbled orientation as they should have in poured concrete. However, within a few minutes at Khufu, we found, at the pyramid base, similarly jumbled nummulites in undoubted Eocene bedrock cut by tectonic fractures and unmoved by man. These jumbled fossils are attributed by Aigner (1983) to storm deposition, a straightforward sedimentary interpretation. At the Temple complex of Saqqara, the casing stones and temple blocks are made of very fine-textured, homogeneous, white Tura limestone smoothed to planar surfaces. The blocks are unusually fine and uniform (like Solnhofen lithographic limestone) and show none of the aggregate-matrix texture of all concretes. However, many of the blocks, perhaps a tenth, show pelecypod fossils several centimeters across that have been obviously sectioned by sawing (Figure 11). By the geopolymer theory, these would have been large fossils that fell or were placed in the concrete mix. But if the ancient Egyptians were trying to manufacture such smooth and homogeneous stone for casings, they presumably would have fished out such big fossils - and the fossil cross sections show that, in fact, the Egyptians were able to master the technology for sawing limestone into fitted blocks in 2700 B.C. Figure 9. Funerary Temple of Khafre. Block shows fine sedimentary layering at the top and a spongy weathering zone in upper middle. Figure 10. Outcropping nummulite limestone in bedrock at the base of Khufu Pyramid. Jumbled orientation of shells is typical of this limestone bed, and similar blocks are seen within the pyramid. They do not indicate a poured concrete origin.

5 Figure 11. Temple wall block at Saqqara. When the Egyptians sawed this Tura limestone block, they cut right through a large pelecypod fossil, whose inverted geopetal filling shows that the block was laid in stratigraphically upside-down. Some thin calcite-filled tectonic fractures are visible (arrows), but there is no calcite filling between the closely fitting blocks, nor is there any filling in the post-construction fracture that mars the left side of the block. Rock Texture and Composition The geopolymer theory requires that disaggregated limestone be mixed with other natural chemicals that react to form a zeolite-type binder. By the laws of packing, carbonate grains should form 65 to 75 percent of the rock, with the rest of the volume taken up by geopolymer binder plus pore space. Pyramid blocks, having undergone almost five millennia of weathering, should show a clear erosional differentiation between carbonate and geopolymer, and chunks of crushed limestone with fossils should be easily seen in the stones in an obvious particle-binder relationship. We saw no such texture in the field, whether on a scale of gravel or sand, even with the use of a 50X hand microscope. A thin section of genuine pyramid stone should solve the problem, but we have as yet been unable to obtain authorization for sampling from Egyptian authorities. A small sample of Khufu pyramid casing stone was graciously given to Campbell by Drs. Tite and Middleton at the British Museum in London in The sample was examined by microscopy, X-ray diffraction, DTA, and chemistry. Two results were particularly significant: 1) No geopolymeric binder could be found either microscopically or by X-ray diffraction. The casing stone was seen to be composed of siltsize particles of calcite of various origins, with minor amounts of terrigenous quartz, feldspar, and clay, plus secondary gypsum and chalcedony. No zeolite cement was observed in the ultra-thin section. 2) Chemical analysis indicated that the limestone consists of only 0.74 percent AI2O3, 0.10 percent Na20, and 8.02 percent Si02 - hardly a composition to be expected had the ancient Egyptians added Nile River silt and natron to the mix. If any zeolite were present, it would have to have been there in minuscule amounts, certainly not enough to be an effective binder. Emery (1960) megascopically identified three different types of limestone and one type of sandstone used as pyramid core stones and pointed out that one limestone variety (mainly used on Khafre) was highly jointed. Recently, we have obtained a copy of Klemm and Klemm (1981), which gives a very thorough analysis of pyramid stones, and demonstrates clearly that most pyramid core stones chemically match the rocks from adjoining quarries, and the casing stones chemically match Tura limestone from quarries near Helwan. JD in 1988 avoided citing this definitive study, though he has been familiar with the Klemms' work since Davidovits sent us a piece of his best effort at imitating pyramid stone, a mixture of mud-size disaggregated carbonate plus zeolitic binder, forming a dense, hard, whitish, synthetic "rock" that, even to a geologist with a hand lens, is very similar to a real lithographic limestone. In a thin section of normal 30 mm thickness, his geopolymer stone closely resembles a natural limestone. Only on very thin edges (less than 5 jim thick) can the contrast be seen between the micron-sized, highly birefringent carbonate specks and the isotropic zeolite binder with a refractive index well below that of the Epoxy mounting medium; magnifications over 400X are required. Gentle etching with HCI removes the carbonate and the zeolite binder can be detected clearly. So, Davidovits has in fact been able to make a good, hand-specimen type of imitation lithographic limestone, but with careful microscopic work it is readily distinguishable from natural limestone. We had several pieces of Egyptian limestone on hand to make comparisons; the true limestone from outcrop had a micrite texture with scattered small forams and other fossil bits, but had substantial microporosity in place of the zeolite binder of the geopolymer. Again, an ultra-thin section is required for proper study of such fine-grained materials. With SEM study it is also very easy to discriminate between Davidovits' geopolymer imitation and Egyptian limestone. Under the electron microscope the natural limestone from Tura can be seen to be made up of tiny 1-10 ^m crystals of calcite with a few dolomite rhombs (Figure 12A). The important thing is the very high micro-porosity between crystals (pores in the jim range), amounting to roughly percent. The rock has virtually no calcite cement, which is why it is so easy to shape into blocks and to saw. In sharp contrast, Davidovits' hardened geopolymeric "limestone" has ill-defined crystals in the 1-2 ^m range within a solid, glue-like matrix of geopolymer cement (Figure 13A). Except for the large spherical, smooth air bubbles ( mm diameter), there appears to be no porosity. To make an analogy, the real limestone samples look like a heap of children's building blocks dumped together with no binder, while the geopolymer looks like a pile of building blocks over which one had poured a large quantity of molasses. A brief acid etch (10 seconds, 10 percent HCI) makes a much more diagnostic characterization of geopolymeric "limestone" (Figure 13B). The carbonate particles etch out rapidly, leaving holes about 1-2 ^m in diameter in the massive geopolymer matrix, like holes in Swiss cheese. The geopolymer etches more slowly, to a smooth glue-like surface, and gives an EDAX pattern for K, Al, and Si. The mica flakes, quartz silt, and so forth, protrude as insoluble components. In summary, the natural limestone consists of a highly microporous aggregation of distinct and uncemented carbonate grains and crystals, while the geopolymeric "limestone" in thin chips under the light microscope shows the carbonate in a matrix of low refractive index and low birefringence, and in the SEM reveals carbonate particles embedded in a glue-like material that is easily identified, especially if etched. Certain other available carbonate samples from ancient archeological structures (see Figure 12B) also consist of natural micro-porous aggregates of 1-10 jum carbonate grains, just like the Tura limestone and other chalky limestones. Geophysical results by Lakshmanan and Montlucan (1987) show that the density of the pyramids (2.05) is very similar to the density of the local Giza bedrock (2.07); with calcite having a density of 2.71, this implies that both bedrock limestone and pyramid blocks have a porosity of around 25

6 Figure 12. Electron photomicrographs, all at the same scale, showing untreated fracture surfaces. A, natural Eocene Tura limestone, from outcrop near Helwan. B, ancient construction block from Giza area. Both samples consist of a loosely packed aggregate of 1-5 mm carbonate particles with a very high microporosity. The natural limestone and the block used in temple construction are virtually indistinguishable. Figure 13. Synthetic geopolymer, imitation limestone concocted by J. Davidovits. Same magnification as the electron photomicrographs in Figure 12. A, untreated fracture surface. Because micron-sized carbonate grains are embedded in a zeolitic geopolymer "glue11 they do not stand out and the surface seems rather flat and featureless, showing no evident porosity. B, slightly etched with HCI. 1-5 mm carbonate grains have dissolved out to leave black holes, quartz and mica bits protrude as white chunks, and the geopolymer binder has dissolved at an intermediate rate to leave a smooth glue-like surface. Thus on both fractured and etched surfaces, geopolymer imitation "limestone11 is readily distinguishable from true limestone. Pyramid blocks are not geopolymeric. percent, in agreement with our SEM observations. Davidovits (p. 187) claims that the low density indicates a geopolymeric origin. A fundamental and obvious objection to the geopolymer theory is that, had the Egyptians wanted to make "permastone," why would they have gone to the excessive labor of crushing limestone and gluing it back together when it would have been enormously easier to use the abundant, nearby desert quartz sand that would have surely made a more homogeneous "concrete"? Bubbles Plaster and concrete typically contain abundant millimeter-sized spherical to irregular bubbles owing to air entrained and trapped during the mixing process. All samples of geopolymer that Davidovits showed Folk in his French laboratory have spherical to ovoid bubbles (Figure 14). Such voids were not seen either in out-cropping limestone or in samples of pyramid stone that we examined with hand lens. The absence of spherical bubbles in pyramid blocks is a tiny, detailed feature, yet nevertheless, deals another devastating blow to the geopolymer theory. Some years ago, the famous French Egyptologist JeanPhilippe Lauer gave Davidovits a sample of pyramid stone thought to have been taken from the Ascending Passageway of Khufu. This sample is one of the kingpins of evidence in favor of the geopolymer theory because, according to Davidovits, it contains small elliptical bubbles and a filament thought to be a hair. If so, this proves that the stone is manmade. But the question then devolves to: Is this chunk a piece of true pyramid core or casing stone, or is it a thick piece of plaster coating? As this evidence is so critical, Folk tried for

7 Figure 14. Davidovits' geopolymeric imitation "limestone." SEM view showing the spherical air bubbles characteristic of man-made plaster, mortar, and concrete. Real limestone does not have such spherical bubbles, nor do pyramid and temple blocks in Egypt. Figure 15. Step-pyramid of Dzoser, Saqqara. Morris' fingers indicate a nearly vertical, calcite-filled tectonic fracture. several years to get Davidovits to mail or bring the specimen for examination. When Folk visited Davidovits in France in January 1990 for the specific objective of inspecting this Lauer specimen, Davidovits said at that time that he no longer had it, but a few months later showed it to several other American geologists. We await their findings. Tectonic Fractures Despite Davidovits' contention to the contrary, there are tectonic fractures in many pyramid and temple blocks, and they are filled with calcite (Figures 2, 11, 15, and 16). These fractures generally are only about 1 mm wide and run in a more or less straight path all across a single block. We have never seen a fracture of this type that continued from one block to an adjoining one. Most weather in high relief on the pyramid blocks, while a few are recessed. These fractures are obvious tectonic fractures formed when the bedrock was flexed millions of years ago and demonstrate that the pyramid core stones were quarried limestone blocks, not poured geopolymer. In contrast, fractures developed upon subsidence after the pyramids were built should be empty or at most only partly filled, and we did in fact observe some of such late, Figure 16. Block of Tura limestone in the Courtyard of Dzoser Pyramid, Saqqara. This block is cut by swarms of nearly vertical, calcite-filled tectonic fractures and is obviously not geopolymer stone. Morris' fingers for scale. Figure 17. Temple walls, near Pyramid of Unas. Limestone blocks are fitted together using many sloping contacts, hardly likely if one were pouring blocks into molds. empty fractures (Figure 11). Modern Portland-cementconcrete replacement blocks tend to be crazed with irregular thin fractures, contain a quartz sand aggregate, and at Saqqara the modern replacement blocks also show impressions of the boards used for forms. At Saqqara, both temples and casing stones show similar tectonic fractures; many of the casing blocks identified as surely original in figure 26 of JD's book show tectonic fractures filled with calcite. In the courtyard facing the pyramid at Saqqara, below the decorative cobras, we saw a quarried block of breccia with wide, calcite-filled fractures. Within the temple at Saqqara there are large, open, post-construction fractures that extend through many blocks. These fractures are devoid of calcite fill, but of course, may have formed at any time during the past 4500 years, probably during reported earthquakes. If an arguement is to be made that calcite cement formed in cracks in geopolymer stone after construction, then why did calcite not also form in the spaces between adjoining casing stone blocks? In fact, many interblock spaces are filled with a red gypsum and sand mortar, easily seen on the Khufu

8 pyramid. If the blocks had been poured in place (JD), why the need for mortar between them? Engineering Problems Besides the geologic evidence laid out above, which proves unquestionably that the Egyptian pyramids and temples we examined are made of real stone, quarried from out crops and hoisted or levered into place, there are several insurmountable engineering-type objections to the geopolymer theory. These include problems with the sizes and irregular shapes of the blocks, problems with making wooden molds for the blocks, and the significance of quarry markings. Shapes and sizes of blocks. A characteristic feature of Egyptian masonry is that the blocks are often not simple rectangles, but instead have sides that slope off-vertical (Figures 5 and 17), and that also extend deep into the wall at non-right angles to the surface. This problem is discussed at length by Clarke and Engelbach (1930). Yet all of these oddly angled blocks fit closely together at the visible surface of the wall. Furthermore, some of the blocks interlock with each other with L-shaped re-entrant corners (Figures 4 and 5). It is utterly preposterous to assume that the Egyptians made wooden molds with such odd angles and shapes. The dimensions of pyramid blocks are cited by Davidovits as strong evidence in favor of the geopolymer theory. He claims to have measured from an enlarged photograph 2000 core-stone blocks high up on Khafre (Chephren) pyramid, and found that they occur with ten discrete dimensions; and still more astounding, he found that blocks of these various dimensions are arranged in a mirror-image array on two faces of Khafre. Despite our repeated requests and a visit to his laboratory in France, Davidovits refused to show us the evidence for this astonishing conclusion. Our own measurements of Khafre block dimensions show that two-thirds of the block widths lie within 25 percent of the mean value; that is, if the mean width was 8 arbitrary units, then two-thirds of the blocks would have widths between 6 and 10 units. This range is so small that it would be very difficult to establish statistically the existence of ten discrete dimensions for blocks (with nine frequency-distribution gaps between). These data must be inspected to be believed. Why would the Egyptian engineers bother to make a set of molds of different sizes in the first place? Why not simply make a wooden mold-side and pour a whole course of geopolymer without septa? In addition, this mirror-image array in the core stones (if true) would have been totally concealed by the outer skin of casing stones. Problems of Molding Technology. Many problems are raised by the pouring of geopolymeric concrete in place on the pyramid sides. First is the matter of chemical reaction time for hardening. M. Payn pointed out to us that a several-ton block would probably take a long time to harden, which could mean a prolonged construction delay if the blocks were poured one after the other. The wide variation in block texture and composition suggests (according to geopolymer theory) a widely varying time required for hardening. If the water is chemically combined as zeolite, the shrinkage-cracking problem is eliminated, but then the resulting geopolymer "stone" should show a large content of combined water; pyramid stones do not. If the geopolymer blocks were cast directly touching the blocks to one side and to their rear, they should adhere tightly to these blocks. But they do not; there are substantial open spaces between separate blocks and in fact some of the wider spaces were filled up by the Egyptians with gypsum plaster (Emery, 1960). However, if mold boards were used on all four sides, it would have been impossible to extricate the boards from between the blocks to the one side and the rear. Further, we have not seen any impressions of wood grain that would result from a molding process, even on fine, well preserved casing stones at Saqqara. The worst problem is that of the bottoms of the blocks. Had mold boards been used on the bottom, they would have been impossible to extricate, and we should see their remains today. If, on the other hand, no bottom boards were used (as JD implies), then the new geopolymer pour should have adhered tightly to the blocks beneath, and it should also have oozed into the spaces between underlying blocks to produce a projecting rib along the joint beneath. Instead, there are crevices on all sides between pyramid blocks, and the bottoms do not show any ribs. In fact, we observed numerous examples of gypsum mortar filling irregular spaces along horizontal contacts between blocks (Campbell and Folk, 1991, figure 10). All this evidence points to the hoisting and placement of large blocks of solid limestone and denies any possibility of their having been poured in place. Quarrying Marks. Davidovits and Morris (1988, p. 57), quoting work by D. Klemm (which we have not seen), asserts that there is evidence of quarry-tool marks only on blocks and quarries younger than 1660 B.C., and that there are no known quarry marks older than that. Therefore, he claims the Egyptians did not yet know how to quarry large blocks and instead must have used the geopolymer formula to make molded artificial stone. This is clearly ludicrous, as the Klemms' work pertained only to sandstone quarries (JD, 1988, p. 57) and Klemm has personally observed quarry marks in Old Kingdom limestone quarries and blocks (personal communication, 1991). Quarry marks consist of parallel, slightly arcuate rows of grooves a few centimeters apart, made by some sort of pick (Figure 18). Marks made by similar techniques occur at the Rameses-age (1300 B.C.) quarry at Khafre, and were made in the 19th century by Italian quarry workers and by stonemasons in Central Texas. At the south side of the pyramid of Khufu, there is a pit that the Egyptians dug into carbonate bedrock during the 4th Dynasty, into which they placed Khufu's funeral barque. The sides of this boat pit and the huge limestone slabs that originally concealed it are covered with similar quarry marks (see photo in Fakhry, 1969, figures 62-63). Similar quarry marks are seen on the sides of many pyramid blocks at Giza (Figure 18B), and on the gigantic stones of the Valley Temple of Khufu (Figure 18C). Aigner (1982, figure 6) shows quarry marks on a temple block and a partly quarried outcrop block, and Emery (1960) found quarry marks on the denser limestone blocks, which tend to be concentrated at pyramid corners. Thus, there is no doubt that the IV Dynasty Egyptians did indeed have the technology to quarry from outcrop, move, and hoist enormous blocks of limestone. The geopolymer theory can offer no rationale for quarry marks on the sides of pyramid blocks that match quarry marks of the same age in the excavations for the boats. Hard Stones. Davidovits and Morris (1988, p. 119, 136, 186, 197, and 200) suggest that the Old Kingdom technicians were even able to make imitation granite, porphyry, diorite, and so forth, by agglomerating igneous minerals and pouring them into molds. This follows their hypothesis that the early Egyptians did not have the technology to cut hard stones; therefore, they must have agglomerated them like concrete. This is preposterous; we have seen many Old Kingdom statues, vases, and granite blocks, and their textures as seen with a hand lens are those of normal crystallized igneous rocks, not of a crystal mush bonded by geopolymer cement. Of course, we have not been able to sample these art objects for thin sectioning. The fact that large granite blocks in Old Kingdom temples contain occasional dikes, veins, and xenoliths did not convince Ms. Morris of their geologic origin.

9 Figure 18. Quarrying marks, made by some sort of pick. A. Ramessid quarry walls at Khafre. B. Block of the Valley Temple of Khafre. That the Old Kingdom Egyptians did in fact have the technology to saw and polish hard igneous rocks is shown by the broken sarcophagus in the Cairo Museum. Saw marks (ridges and grooves) are spaced 1-2 mm apart on the sides of the slot, formed as workmen were trying to saw the lid off the coffin base (Figure 19). Details of this sawn surface are given in Campbell and Folk (1991). Saw marks pass equally well through both quartz and feldspar crystals. Saw marks produced in granite and basalt by ancient Egyptians have been pictured by Clarke and Engelbach (1930, figure 247). If the ancient workmen were able to saw granite, they surely were also capable of sawing soft limestone. The Chinesepuzzle-like fit of huge granite blocks in the Valley Temple at Giza shows that the Egyptians had the technology to fit sawn blocks so closely together that one cannot insert the proverbial knife blade between the blocks. For a people who undoubtedly possessed the technology to saw granite, there was surely no need to glue disaggregated granitic particles together to make fake rock. Conclusions We have marshalled an overwhelming array of facts from both geologic and engineering aspects to show that the geopolymer theory of Joseph Davidovits for temple and pyramid construction, even if it was a brilliant theoretical achievement, does not stand up to the test of evidence. We have- also shown how geologic common sense can destroy archeological quackery, but not, unfortunately, before it has enjoyed widespread publicity among the gullible and sensationminded. The geopolymer theory was based largely on laboratory study of only two samples (Davidovits and Morris, 1988, p. 85 and 88), and brief site visits combined with geologic ignorance and engineering navvete. Rampant yet ingenious speculation combined with brilliant theoretical reasoning led to total disregard for any contrary opinions expressed by professional archeologists and geologists. We believe that archeology is a science that must be based on hard evidence. Not one of our observations favors the geopolymer theory, and our geologic and engineering evidence appears to us to be overwhelming and irrefutable. The geopolymer theory is defunct; we still remain in awe of the enigma of Egyptian skill at engineering. Acknowledgements We gratefully acknowledge Marshall Payn of the Epigraphic Society who is responsible for our field visit to Egypt. We also thank Margie Morris for the pleasure of her company Figure 19. Old Kingdom granite sarcophagus, Cairo Museum. This is a sidewise-flashlit view of the saw slot, showing 1- to 2-mm-wide flat-topped ridges bounded by grooves caused by sawing neatly through quartz and feldspar crystals. This is an incredible technological feat for four millennia ago, but proves that the Egyptians could indeed saw hard rock. in the field and for her stimulating and feisty defense of the geopolymer theory by correspondence and telephone. Intelligent opposition serves to add backbone to any hypothesis. Julie Stein of the Archeological Geology Section of the Geological Society of America graciously permitted us to publish this paper outside of her Symposium. Rosemary Brant did the communications processing, and David Stephens converted color slides (most taken with a 1950 Argus) to black and white prints. References Aigner, Thomas, 1982, Zur Geologie und Geoarcheologie des Pyramiden plateaus von Giza, Aegypten: Natur und Museum, v. 112, p Aigner, Thomas, 1983, Fades and origin of nummulitic buildups: an example from the Giza pyramids plateau (Middle Eocene, Egypt): Neues Jahrbuch fur Geologie und Palaontologie Abhandlung v. 166, p Bianchi, Robert S., 1989, Book Review: The Pyramids: an enigma solved by J. Davidovits and M. Morris: Archaeology, v. 42, no. 4, p

10 Campbell, Donald H., 1986, Microscopic examination and interpretation of Portland Cement and Clinker: Skokie, Illinois, Construction Technology Laboratory, 128 p. Campbell, Donald H., 1988, Analysis of a sample of the Egyptian Cheops Pyramid: Preliminary Report to the British Museum, London, 17 p. (unpublished) Campbell, Donald H., and Folk, Robert L, 1991, The ancient Egyptian pyramids - concrete or rock?: Concrete International, v. 13, no. 8, p Clarke, Somers, and Engelbach, R., 1930, Ancient Egyptian masonry: London, Oxford University Press, 242 p. Davidovits, Joseph, 1987, Ancient and modern concretes: What is the real difference?: Concrete International v. 9, no. 12, p Davidovits, Joseph, and Morris, Margie, 1988, The Pyramids: an enigma solved: New York, Hippocrene, 263 p. Emery, Kenneth O., 1960, Weathering of the Great Pyramid: Journal of Sedimentary Petrology, v. 30, p Fakhry, Ahmed, 1961, The Pyramids: Chicago, University of Chicago Press, 260 p. Folk, Robert L, and Campbell, Donald H., 1990, Egyptian pyramids: geopolymer concrete cast-in-place or true sedimentary rock? (abs.): Geological Society of America Abstracts with Programs, v. 22, no. 7, p. A152. Klemm, Rosemarie, and Klemm, Dietrich, 1981, Die Steine der Pharaonen: Munich, Staatliche Sammlung Aegyptischen Kunst, 48 p. Lakshmanan, Jacques, and Montlucan, Jacques, 1987, Microgravity probes the Great Pyramid: Geophysics: "The Leading Edge" of Exploration, v. 6, no. 1, p Starr, Douglas, 1983, The pyramids, a bold new theory: plastic megaliths: Omni v. 5, no. 5, p , About the Authors Robert L Folk is Carleton Professor Emeritus in the Department of Geological Sciences, University of Texas at Austin. He received all his degrees at Penn State College, specializing in sedimentary geology of the old-fashioned sort (field and microscope), and for 45 years has been an ardent student of limestone. He has also worked on several projects in archeological geology (Yugoslavian Macedonia, Israel, and S. Italy), and is a sub-professional pasta chef. Donald H. Campbell has been with Construction Technology Laboratories since 1975, and is now Principal Petrographer. He has authored many publications on concrete mineralogy, petrography, and its eventual deterioration. He earned three geology degrees, BS at Oklahoma University, MA at University of Texas, and PhD at Texas A & M. He is a member of the Society of Economic Paleontologists and Mineralogists, American Society of Testing and Materials, and International Cement Microscopy Association. Comment On invitation from Dr. Robert L. Folk, I take this opportunity to append a few remarks to the article entitled "Are the Pyramids of Egypt Built of Poured Concrete Blocks?" by R.L. Folk and D.H. Campbell. At present I am actively involved in research on the Giza Plateau and have personally visited the site on more than one occasion. My research involves refining our understanding of the geologic and geomorphic history of the Giza Plateau, including the weathering history of the ancient structures erected on the site. Consequently, the Davidovits hypothesis - that some or all of the ancient structures are composed of poured geopolymer synthetic stone rather than natural rock has a direct bearing on the work I am engaged in. Geopolymers might be expected to weather somewhat differently than the natural limestones of the plateau. The Davidovits hypothesis can be presented in two extreme versions, what I here label the "strong" and "weak" forms of the hypothesis. The strong form holds that virtually all of the classic Third and Fourth Dynasty pyramids and associated structures are composed almost entirely of geopolymer blocks. The weak form of the hypothesis merely contends that Old Kingdom Egyptians were capable of producing high-quality geopolymers and used them occasionally, perhaps for some fine "stonework," but not necessarily for the bulk of the pyramids. When Folk and Campbell state that they knew "within the first minute" of their arrival at Khufu's pyramid that the pyramids (presumably all pyramids, since they use the plural) are constructed of real limestone and thus the Davidovits hypothesis is wrong, they must be referring to a strong form of the hypothesis. A weak form of the hypothesis could not be falsified in only a minute of on-site inspection, or even in only a week of inspection. Indeed, it is virtually impossible to falsify the weak form of the hypothesis short of inspecting every single block of every single ancient Egyptian structure and confirming that all are definitely natural stone. Even such a procedure would not literally falsify the weak hypothesis perhaps all the blocks composed of geopolymer have been lost or destroyed. Of course, the failure of a hypothesis to be falsified does not necessarily corroborate it (much less demonstrate it to be correct). I agree with Folk and Campbell inasmuch as in the field all purported rocks (both sedimentary and igneous) that I have observed in the pyramids, temples, and other ancient Egyptian structures bear all the expected characteristics of natural rocks (such as those described by Folk and Campbell in their article). These rocks also weather in an identical fashion to the undoubted natural bedrock. To date, I have seen no rocks on site in Egypt that I would accept as representing geopolymeric synthetic stone. But, as noted above, failure to observe definitive geopolymeric synthetic rock on site does not ultimately falsify a very weak form of the Davidovits hypothesis. To corroborate a weak form of the hypothesis all that is needed is one good sample of ancient Egyptian geopolymeric stone. Joseph Davidovits and Margie Morris believe they have such corroborative evidence in the form of the Lauer specimen. This specimen, described and illustrated in Davidovits and Morris (1988) presumably came from the ascending passageway of Khufu's pyramid. Several authorities, including Dr. Edward J. Zeller of the University of Kansas Space Technology Center, have suggested that this specimen is not a natural piece of limestone (letter from Zeller to Morris dated 19 September 1990). I have seen a small chip and a thin section of the Lauer specimen, and I would not characterize it as plaster (as Folk and Campbell suggest in their article). I cannot rule out the possibility that the Lauer specimen consists of natural stone (though apparently not one of the typical limestones that compose the bulk of the ancient structures on the Giza Plateau). Robert M. Schoch College of Basic Studies Boston University 871 Commonwealth Avenue Boston, Massachusetts 02215