Mansoor Amarna Collection

Dr. Richard L. Hay Report

From the University of California, Berkeley

I have completed my petrographic and mineralogic examination of two sculptures from El Amarna. One of these is a fragment of a bust, weighing 408.4 g, and the other is a head weighing 518.2 g. The aim of this study was to determine the nature of the material of which these figures were made, with the particular object of proving whether or not it is a manmade material ( artificial stone ). I have done no further work on the evidence of surface weathering, that has been ably documented by other scientists ( see Stross, 1960; Stross and Eisenlord, 1965 ). The fragment of bust was studied by a wide variety of laboratory methods, some of which are destructive, with the object of determining critical observations which could be made on the head with minimal destruction.

Fragment of bust

The fragment of bust is of a somewhat chalky, very fine-grained limestone mottled light reddish brown and pinkish gray ( Munsell color system ). This was studied as follows :

1. A portion ( approximately 15 g ) was sawed off, reaching to a depth of about 1 cm into the interior. From this sawed slab a thin section was made and studied with the petrographic microscope at magnification up to 360 x. This method is ideal for determining microscopic textural details down to a size of about 2 m ( microns ).
2. The figure, including the sawed surface, was studied under a binocular microscope. This is vital for studying microscopic features in 3 dimensions and determining the location of the iron oxide giving the rock its reddish hue.
3. A 7.8 g portion of the sawed slice was dissolved, without crushing, in a solution of acetic acid buffered by lithium acetate at a pH of 4.5 which is only slightly more acid than rainwater. This was done to obtain the clay-mineral fraction, other minerals such as dolomite, and possible artificial " glues " or cements ( e.g. portland cement ) that would either be modified or dissolved in a strong solution of a strong acid. Because of the buffering, this method is non-destructive to nearly all water-insoluble substances other than calcite. The acid-insoluble residue was examined microscopically.
4. An X-ray diffraction pattern was obtained both from a ground sample of the figure and from acid-insoluble residue. X-ray diffraction is a foolproof method of identifying all crystalline materials, regardless of particle size, that are present in amounts of at least 1-2 percent.
5. Fossils in the sample were examined by Gordon Horaday, the foraminiferal specialist of the Museum of Paleontology at the University of California at Berkeley.

Results of his work are summarized below :

Microscopic study. The rock is a limestone consisting of delicate calcareous micro fossils ( foraminifera, hereafter termed forams ) in a matrix of clayey, very finely crystalline calcite, termed micrite by geologists. The forams are chambered tests, most of which are less than .25 mm in diameter. Most are intact ( unbroken ), but fragments of tests can be seen in the micrite matrix. A very small amount, probably on the order of one percent, of well-formed rhomb- shaped dolomite crystals are present, both in the matrix and in the chambers of the forams. The rhombs range from about 2 m to 30 m in length. Some of the foram chambers are filled by calcite, with or without reddish ferric oxide and dolomite. Most chambers are unfilled. The porosity is estimated to be 20- 25%, with most of the pore space in chambers of the forams. Permeability is low because few of the larger pores are interconnected. This is an excellent, typical example of a pelagic (open-water, marine ) limestone. Limestones of this type are common in the geologic record, and its modern ( unconsolidated ) equivalent is in the so-called Globigerina ooze which covers much of the sea floor.

Internal textural details are diagnostic of a natural limestone resulting wholly from geologic processes. The delicate preservation of thin-walled tests shows that no pressure could have been applied before the sediment had consolidated. Some of the intact, unfilled, chambered forams have walls only 1 micron thick ! Similarly sheetlike test fragments 100 microns long and only 3 microns thick are unfractured. The reddish pigmentation is caused chiefly by dark reddish-brown ferric ( i.e. iron ) oxide staining fragile aggregates of calcite crystals inside foraminiferal tests. Similar colored calcite is not found in the matrix of the rock. This iron oxide was produced by slow ( over geologic time spans ) redeposition of the iron within the parental limestone bed. It could not have been introduced as a pigment to some sort of artificial mix. Finally, dolomite rhombs must have grown in situ, within the rock, as shown by their euhedral (bounded by crystal facies ) shape and occurrence within tests and growing into open pores. Dolomite crystals of this type are common in marine limestones of this type which are on the order of 10,000,000 years old ( or more ). An artificial ( i.e. man-introduced ) origin is ruled out, as this requires either the introduction of dolomite powder to an artificial mix, or the synthesis of dolomite crystals within the consolidated synthetic stone. The only likely source for small dolomite crystals in an artificial mix would be to crush natural dolomite. Crushing inevitably produces a much higher percentage of non-rhombic fragments than of rhombs of the size and shape found in this specimen. In one crushing experiment, I got only no more than 5 percent rhombic cleavage fragments similar in shape to the dolomite crystals in the limestone. Moreover, this process cannot account for the dolomite crystals inside chambered tests. As for the alternative ( synthesis within the limestone ), dolomite is extremely difficult to synthesize, particularly at temperatures below 200o C, and the synthetic dolomite is invariably finer-grained than the coarser crystals in the rock, and it is most generally structurally different ( a " protodolomite " ) from that which crystallizes naturally over millions of years. Moreover, the limestone is relatively impermeable, and remarkable technology would be required to avoid higher concentration of dolomite in the margin than in the interior of the figure.

X-ray diffraction .

X-ray analysis of the bulk sample shows that it is almost entirely calcite, and the remainder comprises small amounts of clay mineral, quartz, and dolomite. Clearly there are no exotic compounds such as calcium silicates or sulfates ( of mortar, concrete plaster, etc.) . X-ray analysis of the acid- insoluble fraction shows that the clay mineraly has a 14.2 A ( angstrom ) basal ( 001 ) spacing and is of the montmorillonite ( = smectite ) family. Quartz and dolomite are also present, as to be expected.

Acid-insoluble residue. It should be stressed that dissolution of this limestone in a solution of acetic acid buffered at a pH of 4.5 is generally non-destructive of anything other than calcite ( anything, that is, that is not soluble in water ). Microscopic study showed only clay mineral, quartz, dolomite, tiny fragments of fish bones, and trace amounts of a few other minerals. No foreign substances ( organic cements, glues, etc.) were present.

Paleontologic determination. The fossils of this limestone are foraminifera of the category Globigerina. The bulk of these are probably of the genus Globorotalia ( Eocene, 40 to 60 million years ago ), although Globotruncana, of Cretaceous age ( about 70 to 125 million years ago ) is not precluded without additional sectioning and microscopic study. An age more recent than Eocene is absolutely precluded.

Summary and analysis.

I have gone farther than necessary in documenting what is really a simple matter. The intact nature of the delicate foram tests together with the euhedral shape of dolomite crystals shows that this limestone could not have been made by cementing crushed limestone; it must have been made by consolidation of globigerina ooze in situ ( without application of pressure ). It can perhaps be conjectured that a technology might exist ( say by beings from another planet technologically much more highly advanced than Homo sapiens) for artificially duplicating the several geologic processes required to transform marine calcareous ooze to a dolomite, ferruginous limestone of this type. However, a limestone of this type would necessarily contain modern types of forams,as unconsolidated deposits of Eocene(or Cretaceous ) forams, particularly of this delicate degree of preservation, no longer exist, either on the land surface or on the sea floor.

Head

The head is of a pink to pinkish gray color and is a chalky, foraminiferal limestone similar in appearance to the fragment of bust. Chips as much as a millimeter thick were taken from the base of the figure for the purpose of studying under immersion oils with the petrographic microscope. The thin edges of chips can be studied in the same way ( although with less ease ) as a thin section. A relatively large chip was dissolved in acetic acid buffered at a pH of 4.5 to obtain the acid-insoluble residue. Both the surface of the head and the interior as exposed by chipping were studied with a binocular microscope. It is of the same type of Eocene or Cretaceous pelagic limestone as the fragment of bust. A few distinctive features are listed :

1. The forams are of the same intact nature and biological type as those of the bust ( i.e. Globorotalia or Globotruncana ). Most of these are unfilled or partly filled by calcite stained reddish brown by iron oxide, as in the bust
2. The porosity and permeability are similar to those of the fragment of bust.
3. The acid-insoluble fraction contains clay, small euhedral dolomite crystals, and a very small amount of quartz, etc. It is similar to the acid-insoluble fraction of the fragment of bust in all significant respects.

Unquestionably this is a natural limestone, almost certainly from the same deposit as the fragment of bust. In an earlier report, some highly tentative evidence of fatty acid or organic residue was used as an argument for an artificial origin. An organic residue, even if correctly identified, has no bearing on the natural vs. artificial origin of the limestone. Nearly all limestones naturally contain organic residue ( especially hydrocarbons ). One expert in carbonate rocks has estimated the average amount in limestone to be about 0.2 percent ( see p.43 in Blatt, et al.,1972, Origin of Sedimentary Rocks, Prentice Hall ) .