More than most technical procedures in the ancient world, drilling of hard stone such as quartz and granite has evoked awe and puzzlement. Neither wall paintings, nor textual information, nor excavated material has provided complete answers as to how drilling was done. As a consequence, there has been scholarly controversy. One such disagreement occurred between two eminent Egyptologists, A. Lucas and Sir Flinders Petrie. Their argument revolved around a difficult and important question, namely, how did the ancient Egyptians of the 3rd millennium B.C. drill granite?
1a. The granite core published by Petrie was made by the ancient Egyptians using a tubular drill. Note the similarity of the concentric lines (arrow) found on the core.
This unresolved question, raised by Petrie as early as 1883, is important not only to Egyptologists, but to scholars of ancient lapidary technology anywhere in the world where hard stone was drilled. Here, we report on our preliminary experiments directed toward a resolution of this controversy. The reader must bear in mind that our work is based solely upon the evidence of the object examined, and does not take into account ancient Egyptian textual or material evidence that might shed light upon this problem.
The disagreement between Lucas and Petrie can be most accurately summarized by alternately juxtaposing their own words written over a 35-year period.
Lucas:
“…as neither copper nor bronze is sufficiently hard to cut such stones as basalt, diorite, granite, quartzite and schist, a harder material than the metal is required to do the work which must have been used either in the form of [fixed] cutting points [teeth] or as a loose [abrasive] powder . . . in my opinion, it was a loose abrasive powder [of] finely ground quartz sand used wet … loose quartz sand which occurs in great abundance in Egypt and will abrade quartz … which was the hardest stone the ancient Egyptians worked.”
Petrie:
“The cutting of granite was done by jewelled tubular drills . . . with cutting points . of emery . .. set in the sides of the tube both inside and out . .. every mechanic who has examined the grooves on .. . a core of red granite from Gizeh agrees that nothing but a fixed point could have cut such grooves.”
Lucas:
“In my opinion to suppose the knowledge of cutting these gem stones to form teeth and of setting them in the metal in such a manner that they would bear the strain of hard use and to do this at the early period assigned to them, would present greater difficulty than those explained by the assumption of their employment . . It is highly probable that pieces of the abrasive would have been forced into the metal, where they might have remained for some time . . and produced the same effect as intentional and permanent ones.”
Petrie:
… It seems physically impossible that any particle of a loose powder could become so embedded in a soft metal by the mere accidents of rubbing that it could bear the immense strain needed to plough out a groove of any considerable depth in such a hard material as quartz. … Modern diamond drill cores are clumsy and smudged work when compared to the Egyptian cores.”
1b. produced by a modern mason’s diamond tubular drill.
In essence, then, Lucas and Petrie, looking at the same regular concentric lines on drilled cores of granite (Fig. 1), disagreed as to whether they were made using a loose wet quartz sand abrasive (Lucas), or fixed points of emery (Petrie). (Note: Emery is a granular rock composed mainly of corundum—a crystalline compound of silicon and carbon—magnetite and spinel. Here, `emery’ and `corundum’ are used for the abrasive powders derived from these rocks.)
Lucas cited many references to show that quartz sand could drill granite. However, none of these references indicated that concentric lines were formed as a result of the drilling. Petrie speculated that diamond and corundum were used for drilling. He rejected diamond for its “rarity” and corundum for its “impossibility” in favor of emery. Neither cited evidence for his conclusions.
The purpose of our paper is to present experimental evidence which partly resolves this disagreement. Our evidence resulted from the functional analysis of a drilled granite lid from an Old Kingdom sarcophagus ca. 2500 B.C., now in the Brooklyn Museum (Fig. 2). It probably belonged to Prince Akhet-Hotep of Dynasty IV. The sarcophagus weighs about four tons, the lid two tons. The lid has two holes on each end that were (probably) used to raise and lower it. The holes are 24 cm. long; their diameter on the outside is 5.3 cm. and tapers to 4.3 cm. on the inside.
2. Old Kingdom sarcophagus now in the Brooklyn Museum. Note the drill holes at the end of the lid. The lid weighs two tons. The drill holes are 24cm. long. 5.3 cm. diameter on the outside, and taper to 4.3 cm. on the inside.
Method of Investigation
Some of the procedures that we have employed in this investigation have been previously reported. They have been used to analyze (1) beads from Shar-i-Sokhta, an Early Bronze Age site in eastern Iran; (2) ancient Near Eastern cylinder seals; (3) the drilled, inlaid teeth of the ancient Maya; (4) an Early Bronze Age Cycladic statuette, and (5) stone statuettes exhibited at the Cleveland Museum.
There are three separate steps in our method of investigation, all non-destructive to the object. They are (1) silicone impressions of the parts to be studied in order to capture the tool marks; (2) examination of the impressions (or epoxy models made from them) in the scanning electron microscope (SEM) and the fabrication of photomicrographs, and (3) functional analysis attempting to duplicate the tool marks experimentally.
Ordinarily, when taking silicone impressions of a narrow drill hole on seals or beads, a toothpick has been used to tease the loose-flowing silicone into the hole. Because of the size of the drill holes in the lid, we had to resort to a modification.
In order to take an impression of the hole, a large dowel was used instead of a toothpick. Before the addition of the free-flowing silicone, a heavy-based silicone was placed around the end of the dowel and molded so that it was slightly narrower than the circumference of the hole. When this had set, free-flowing silicone was added and the dowel inserted into the hole. When the silicone had set, the dowel was removed first. This permitted the silicone impression to be removed more readily since it could be compressed slightly into the space occupied by the dowel. Because of the length of the drilling, the impression was made in two parts.
3. Silicone impression of the drill hole. The concentric lines are visible (arrow). Similar lines have been found in (and reported on) the central bores of ancient Near Eastern cylinder seals and in early Bronze Age beads excavated in Iran.
4. Photograph of a model of the bottom of the drill hole shows that lines are spaced closer together (arrow). This may be due to abrasive having become finer as drilling continued.
Findings on The Impression
The regular concentric lines are clearly visible macroscopically on the impression (Fig. 3). They are quite similar to those found and reported by Petrie. Several characteristics are obvious from a study of the silicone impressions:
The drilling was done entirely from one end with a relatively slight taper. Over the 24 cm. length of the drill hole there was only 1 cm. or 4% narrowing, indicating very little wear and wobble of the drill. This shape suggested the use of a tubular drill and will be discussed later. The concentric lines were aligned more closely near the bottom or narrow end (Fig. 4). The concentric lines were not always perfectly parallel. Occasionally a line tracked at an angle across adjacent lines (Fig. 5). Some of the lines exhibited a slight amount of irregularity. At the edge of the narrow end of one of the holes, there is a region devoid of lines, slightly rounded and having almost a polished appearance (Fig. 6).
Functional Analysis