摘要:

Mechanical testing of lithologies used for stone tool manufacture has shown that fracture toughness is the most objective measure of the quality of raw materials shaped by either flaking or pecking/grinding. Materials amenable to pressure flaking and blade manufacture have low values of fracture toughness, whereas those shaped by pecking/grinding have high values. The fracture toughness test is also the most definitive for quantifying the improvement in flaking properties of materials subjected to intentional heat treatment. Cryptocrystalline and macrocrystalline siliceous lithologies demonstrate a well‐defined, gradual reduction in fracture toughness with increased temperature. When heated to optimum temperatures, their fracture toughness approaches that of obsidian, the lithology generally regarded as having the best flaking propertie

ISSN:0003-813X    

DOI:10.1111/j.1475-4754.1994.tb00963.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The recently‐developed laser microprobe40argon‐39argon technique has been used to give a geological date for a rhyolitic tuff stone axe fragment from the Stonehenge environs. The method requires only milligramme‐sized samples and gives dates of sufficient accuracy to aid in provenancing artefacts to sources, as well as information on the heating history of samples. The axe sample is of Lower Carboniferous date (341 ± 5 Ma) and this limits possible sources to outcrops within the Scottish Midland Valley and small altered exposures in Dartmoor. X‐ray fluorescence analysis of the axe suggests the Scottish Midland Valley as the more likely source. The laser argon analysis also shows that the implement had not been heated in antiquity. Laser argon‐argon dating can, therefore, be a useful tool in arte

ISSN:0003-813X    

DOI:10.1111/j.1475-4754.1994.tb00964.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Microprobe and digitized electron‐backscatter image data reveal that eighteenth‐century Bow porcelain consists of a silica polymorph(s) (25–43 vol. %), a calcium phosphate phase (42–55%) with homogeneous and stippled textural variants, and a silicon‐, aluminium‐, and calcium‐rich, former melt phase represented by discrete domains (14–20%) and micron‐scale blebs that occupy 20–70% of the stippled calcium phosphate. Bulk compositions calculated from these data are deficient in calcium phosphate components and more siliceous than those determined by microprobe analysis of fused powders of the same samples. This reflects difficulties in determining representative values for the composition and volume of the melt phase, and underscores the limitations of the method where applied to media containing compositionally‐ or texturally

ISSN:0003-813X    

DOI:10.1111/j.1475-4754.1994.tb00965.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Philistine bichrome ware from Tell en‐Nasbeh, an Israelite village in the hill country, has been characterized by instrumental neutron activation analysis. A group of pottery stylistically indistinguishable from wares made in Philistia is shown to be of local origin, while other sherds match kiln wasters found in the littoral Philistine city of Ashdod. These findings attest to complex and reciprocal interregional contacts between the Philistines and the Israelites during the eleventh to twelfth centuries B

ISSN:0003-813X    

DOI:10.1111/j.1475-4754.1994.tb00966.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Sensitivity, precision and accuracy of quantitative microanalysis of major, minor and trace elements present in ancient glasses by energy dispersive spectrometry (EDS) is compared to that by wavelength dispersive spectrometry (WDS). Although there are certain problems with EDS due to peak overlaps and background noise, the precision and minimum detection limits of EDS for most of the important elements in ancient glasses were found to compare favourably to those of WDS. Both EDS and WDS, when quantified by comparison to glass standards, can produce reliable results which are adequate for most technological questions.

ISSN:0003-813X    

DOI:10.1111/j.1475-4754.1994.tb00967.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Sixteenth‐ and seventeenth‐century European blue glass trade beads from aboriginal sites in the eastern Great Lakes area of North America have been analysed non‐destructively using low neutron dose instrumental neutron activation analysis, so that the beads could be returned to their keepers. Dark blue (cobalt‐coloured) beads are readily separable from turquoise (copper‐coloured) beads. Differences in the chemistries of the turquoise blue beads appear to be useful in separating glass beads from the two centuries. Low calcium, sixteenth‐century turquoise beads tend to distintegrate by a leaching of the al

ISSN:0003-813X    

DOI:10.1111/j.1475-4754.1994.tb00968.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The black inlay decoration with superb marine, hunting and other scenes on Mycenaean bronze daggers and silver cups has often been referred to in the literature as niello—a mixture of sulphides of copper, silver or lead—despite the absence of any systematic analysis of these precious metal artefacts. This paper presents semi‐quantitative surface analyses of an example of black inlay on a Mycenaean dagger, now in the Archaeological Museum at Patras in Greece. Using non‐destructive X‐ray fluorescence spectrometry, it has been established that, contrary to the traditionally‐held view, the black inlay is a copper‐gold alloy with some silver and possibly small a

ISSN:0003-813X    

DOI:10.1111/j.1475-4754.1994.tb00969.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Discriminant analyses of distances and angles obtained from 25 coins struck by P. Crepusius in 82 BC permitted the correct chronology for five groups of closely‐related dies to be obtained by the method of Carter and Frurip. Twenty distances and 15 angles were measured on 10 x projections of the coins which represented five groups of dies separated in time from each other. The use of all or many variables gave poorer results than the use of five to ten variables having a high ‘figure of merit’, defined as the maximum range of mean values for a given variable in the five groups of dies divided by the mean standard deviation of the variable in the five groups. It is recommended that chronologies of ancient coins be determined from Mahalanobis distances by using only variables of relatively high figure of

ISSN:0003-813X    

DOI:10.1111/j.1475-4754.1994.tb00970.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

A statistical procedure for grouping pottery in provenance studies by chemical data is presented, which now is routinely in use in our laboratory. It is based on the Mahalanobis filter method and X2‐statistics, and can be used for both establishing groups and assigning single sherds to already known groups, thus replacing principal components analysis or cluster analysis and avoiding their problems in grouping pottery. The new method is able to consider correlations, uncertainties of measurement and constant shifts of the data in case of dilution. In particular, considering dilution effects results in both a better assignment to and separation of reference groups and is also equivalent to the compositional data approach, if log‐transformed data are used. Other distortions of data (e.g., mixing of clays) can also be conside

ISSN:0003-813X    

DOI:10.1111/j.1475-4754.1994.tb00971.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

This paper argues for cross‐validation to reduce bias in estimating Mahalanobis distances of individuals to groups, a particular problem with small sample sizes. Formulae for the efficient computation of cross‐validated distances, which avoid excessive matrix inversion, are given. The use of Mahalanobis distances as measures of consistency, or as indications of outlying values, is described. The little‐known technique of gamma plotting is outlined and discussed as an aid to interpreting distances in these terms. Both cross‐validation and gamma plotting are illustrated in an example on marble comp

ISSN:0003-813X    

DOI:10.1111/j.1475-4754.1994.tb00972.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY