ホドソン鑑定
サザンプトン大学、地質学者フランク・ホドソン教授の鑑定要旨。アン・ロスが自らの論文に添付したモノ。Appendix Heads 4 and 5, from Hexham, were examined by Professor Frank Hodson,Professor of Geology and Dean of the Faculty of Science in the University of Southampton.
His findings are as follows:So far as can be determined by surface examination both heads are made from the same material which apparently is a very coarse sandstone with rounded quartz grains up to 2mm diameter in a calcite cement.
The head with the incisions representing hair is weathered to show the surface character of the stone admirably.
This material could well have come from the vicinity of Hexham. Officers of the Leeds Office of the Institute of Geological Sciences inform me that such sandstones occur below the Durham “Millstone Grit” and especially in a bed just below the Little Limestone, north of Hexham.
This sandstone is not shown on the Hexham Geological Survey Sheet (No. 19) since it was not then the practice to map the thin sandstones in this part of the geological succession.The head with a groove extending from behind the ears over the high forehead, shows the hair region to be particularly smooth—an effect which I doubt could be achieved by polishing such coarse sandstone.
Close examination reveals that a surface coating of fine material has been applied.
Most of this surface is now blackened,perhaps by some altered pigment.The immediate underlying material is an ochreous yellow colour.
Examination of a minute scraping of this by X-ray diffractometry shows it to be calcium carbonate.It thus seems that the head region was plastered over with lime to give a smooth surface.Possibly this was to provide a surface suitable for colouring.
Within this smooth region are small white patches which may more nearly represent the original plastered surface having been protected by “paint” only relatively recently lost.The left eye socket also contains white material which has minute spots of green substance.This is also possibly the same plaster in an undiscoloured condition preserved under a pigment now almost completely lost.
Permission to remove a fragment would be necessary to determine the exact nature of this “eye” but, whatever the substance, it has been inserted whilst plastic and is not a specially shaped “jewel” inserted in the socket.
ダグラス・ロブソン鑑定
ニューキャッスル大学ダグラス・ロブソンによる鑑定結果。『Quest for the Hexham Heads』より。REPORT ON HEADS 4 AND 5, FROM HEXHAM
General observations
The material from which the heads have been fashioned consist of uniformly large grains of quartz – 2mm diameter on average – set in a very fine-grained matrix. The latter is calcareous. The grains are extremely well-rounded
and polished, with no indication of partial solution or of secondary growth.
There are numerous sandstones, belonging to the upper Carboniferous succession,which outcrop in the Hexham district, but none of them bear any similarity to the material from which these heads have been formed. Indeed, this material is unlike any natural sandstone.
Specific observations
1.In a natural sandstone, there is invariably a predominance of grains of a particular diameter, but also with a fair proportion of grains of greater and lesser diameters. On analysis, such a sandstone provides a cumulative with one prominent peak. The material of the heads would no doubt form a curve with two marked peaks – something which a normal sandstone seldom provides in nature.
2.In a natural sandstone, the grains are closely packed, and in contact with one another; any fine interstitial material introduced after the deposition of the sandstone, would occupy the small pores between the grains. The material from the heads consists of a large proportion of very fine grained matrix with the very much larger quartz grains imbedded in it but generally not in contact with each other.
3. In a natural sandstone, the quartz grains generally show a considerable degree of singularity; this is certainly true of all the local sandstones. Only sand grains which have been subjected to desert conditions or to intense wave action on a sea-beach show the degree of rounding exhibited by the grains which come from the Hexham heads. Moreover, grains from a desert sand show a pitted, rather than a polished surface.
4. In a natural sandstone, there is generally some indication of bedding or a layering of the grains; no such pattern can be detected in the material from which the heads are formed.
Conclusions.
The material from which the heads have been formed is an artificial cement. The sand grains in it are probably derived from the sea-shore, where wave action sorts out material to a very uniform size and produces a high degree of rounding and polishing. There are often well-rounded calcareous fragments – from sea-shells in such a deposit though, without disaggregation, it would not be possible to confirm this point in the case of the Hexham heads. If the heads are of modern origin, no doubt the quartz grains come from a builder’s sand. If they are of ancient origin, presumably some enterprising Hexham Briton, struggling through the swamps of the Tyne valley, may have visited the seaside and have come back with a satchel of sand which he subsequently mixed with ground-up limestone and water.
There is an adequate local supply of limestone.No further comment regarding the polished surface of the heads, beyond those made by Professor Hodson, needs to be added.