Brief examination was made of several small sculptured articles supplied by Mr. E. Mansoor from his collection. One of these, a head 4 1/2 inches in length, sculptured from a brownish-pink limestone, was examined more extensively.
This author has no experience in art which would allow any opinion as to the authenticity of this head as an ancient object of art. He is, however, experienced in the examination of many materials under ultra-violet light, and in microscopy of surfaces. The examinations were limited to these areas, and to photography of certain surface features of the head.
Previous Reports:
Previous reports that were read included those of W. J. Young; Eliot Blackwelder; Etienne Drioton; Robert E. Compton; Zaki Iskandar and Zahira Mustafa, which included that of A. Lucas; and Robert E. Arnal.
The sole report in which the authenticity of these sculptures is brought into question is that of W.J. Young. His report is chiefly impressive for its lack of reasoned conclusions, and the distinct impression that he is expressing only a personal opinion that he does not believe the sculptures to be genuine; hence, any observation he makes is so interpreted. His conclusions from examination with ultra-violet light cannot be given unqualified acceptance by anyone experienced in the technique.
The additional reports give support to the authenticity of the objects as being of ancient origin, and excellent experimental work and logical conclusions are present to a degree in most of them . It can be accepted that the material is genuine limestone, containing many Foraminifera, and various mineral inclusions other than calcium carbonate. Dendrites of manganic oxide are apparent, more commonly in fissures than on the surface in the specimen examined.
The Physical Problem:
It seems clear that there are only two alternatives : ( a ) the sculptures are genuinely antique, and all effects observed are those of long duration, or ( b ) they were counterfeited in relatively recent times, and all effects are produced by planned, artificial methods. The decision between the two alternatives will be reached when the details are examined in the light of each of them.
( a ). If the sculptures are genuine, they were exposed to a degree of weathering from water and its dissolved constituents, and from wind and particles carried by the wind. In addition, water effects would have been produced on the original rock before it was quarried. Since the storage conditions are not known to the author, it is merely assumed that water effects would be minimized by a desert climate, and that wind effects might be expected to predominate. There is no reason to assume that the effect of water would have been the same on the original rock as it was on the carved objects, since the rock may have come from an environment different from that of final storage of the objects.
The effect of water-borne, eroding materials is most apparent in the patina and in the manganic oxide dendrites. As pointed out in several of the earlier reports, the color of the surface layers is darker than that of the interior of the stone, which is visible at one or two points on the object examined. This color effect is not consistent with the application of coloring matter, as was developed by Robert Arnal and others.
Mr. Young stressed the presence of dendrites within cracks and crevices as an indication that they were existent within the original stone--a point that was easily confirmed. However, there are numerous surface deposits of the same material which protrude above the surface in such a manner as to make it apparent that the surrounding limestone has been eroded away with protection of the small area by the harder manganic oxide. This effect was noted by Professor Compton, who commented on it in some detail. The surrounding erosion appears to this investigator to be most significant, and to favor wind erosion rather than chemical action as the chief factor, as was also indicated by Mr. Arnal.
The surface of the object examined shows definite erosion with resulting protrusion of many Foraminifera, silica particles, manganic oxide and possibly other inclusions. This effect is shown in accompanying photographs. The effect could have been produced by a sort of sand blasting with extremely fine particles, such as the fine material carried by the wind. Chemical weathering also might well have contributed as mentioned by Professor Compton. Nevertheless, the chief effect is one of mechanical erosion, as stressed by Mr. Arnal.
The presence of a patina, which definitely could have been produced by natural causes over a great period of time, along with the mechanical erosion of the surface, provides strong evidence of the correctness of the assumption of genuineness of the objects as being ancient.
( b ). If the objects are counterfeit, consideration must be given to all possible means by which all of the existent effects might have been counterfeited. The items that would require duplication with genuine objects are :
Items l, 2, and 3 are readily available to a counterfeiter. Item 4 would present grave problems. The most practical method would be a very fine sand-blast, which would erode the soft portions of the rock and polish the harder portions. Ordinary sand-blasting would not be effective because the sand is too coarse, and the force too great. Extremely fine material would be necessary, and no ordinary nozzle would make the operation as uniform as is required. It is conceivable that mechanical equipment could be constructed to produce the erosion, but only with great difficulty and expense.
Production of the patina-- item 5 -- presents even greater problems. No speeded-up natural process could be used to obtain so hard and firm a coating. Alternate soaking in carbon dioxide charged water, and drying, would bring mineral to the surface as occurred, but would deposit it in a fragile -- probably powdery -- form that is completely different from the actual situation. This can be ruled out as a practical possibility.
Application of colored substances to the surface has not occurred, nor could the intricacy of the color distribution be reproduced by the methods of the artist. Again, this is simply not possible.
Still more difficult would be the necessity of combining the erosion procedure with deposition of patina. One or the other would have to be done first, and either would tend to spoil the other. It would be necessary to alternate processes, as would occur naturally and, beyond a doubt, the effort to do this artificially would be completely impractical.
Item 6 is not possible except over long periods of time. If the dendrites were formed on the surface, it would itself be proof of antiquity. If they were exclusively internal in the original stone , it would not be necessary to produce them in a counterfeit. Microscopic examination indicates to this investigator that many of the black deposits that presumably represent eroded manganic oxide, were deposited on the surface, but none were sectioned to prove the point.
Items 2 and 3 appear to call for further attention. Any counterfeiter would be constrained to work with as effective tools as possible. He would not be likely to resort to the crude scraping and polishing tools used in antiquity. If this be a true statement of fact, it would follow that the final shaping, smoothing, and polishing would make use of modern abrasives, cutting and polishing wheels, files or rasps, and similar tools. It is a fact that all of these types of instruments leave parallel markings on the object abraded. Such marks could be removed only by very extensive polishing, and if not removed would indicate modern types of tools.
Numerous tool marks are visible on the item examined, as was discussed by Professor Compton. They represent originally deep furrows that were not completely removed by polishing or by subsequent erosion. Some of these are visible on accompanying photographs. None of these could be found in parallel combinations. This may be accepted as virtual proof that they were made individually by a pointed tool of some type. It is not consistent with modern methods of shaping stone rapidly, and may be taken as an additional indication of authenticity.
Summary:
Comparison of the possibilities of genuine antiquity as the cause of the condition of the surface of the object examined with those of counterfeiting of this condition indicates very strongly that the object is in its present condition as a result of long weathering.
The erosion of the surface, along with its patina, could not have been duplicated so precisely by rapid methods without leaving telltale failures and errors that could be located and interpreted.
Not only the surface itself, but the markings on it, the erosion around raised manganic oxide particles, and other detailed features, are all in accord with the genuine antiquity of the object examined.
Submitted this 16th day of March, 1959.
( Paul L. Kirk )