RIETVELD X-RAY DIFFRACTION AND X-RAY FLUORESCENCE ANALYSIS OF AUSTRALIAN ABORIGINAL OCHRES*

Rietveld phase analysis of X-ray powder diffraction patterns and chemical analysis by X-ray fluorescence spectroscopy have been used to characterize a series of red and yellow ochre samples from Aboriginal ochre deposits in South and Western Australia. The ochres were found to have diverse mineralogy, being mixtures of up to seven minerals, and also to have complex trace element signatures. The mineralogical characteristics and geochemistry of the ochres can be used to identify the source quarries. Using this combination of analytieal techniques it may be possible to trace the source of ochres in burial sites and on objects back to the original quarries.     

X-RAY FLUORESCENCE ANALYSIS OF MODERN AND RECENT CHINESE PORCELAINS

X-ray fluorescence analysis of modern and recent Chinese porcelains shows that the Mn/Co ratio is about 2.5 and above for those made before World War II and less than 0.7 for those made after the war.     

NON-DESTRUCTIVE RADIOISOTOPE X-RAY FLUORESCENCE ANALYSIS OF OLD SILVER COINS

The paper presents the results of a feasibility study of the application of X-ray fluorescence analysis to nondestructive analysis of coins. Radioisotope sources ⁵⁵Fe, ²⁴¹Am, ¹⁰⁹Cd and ²³⁸Pu were used for excitation and a Si/Li detector with a multichannel analyser for the measurement of characteristic X-ray lines. Silver and copper in Polish renaissance coins have been analysed. Analysis using Ag K and Ag L lines allows one to distinguish between blanched and unblanched coins. The accuracy of the silver determination using Ag K X-rays is claimed to be ± 0.5% Ag for homogenous coins and ± 1.0% Ag for blanched but well-preserved uncorroded coins.     

X-RAY FLUORESCENCE ANALYSIS OF MUSEUM OBJECTS: A NEW INSTRUMENT

A new X-ray fluorescent analyser is described which uses a miniature X-ray tube or radioisotope source as alternative means of primary excitation. The advantages of this approach as compared to previous methods, particularly where elements low in the periodic table are concerned, is discussed. The second part of the paper describes an application of the technique. The non-destructive analysis of valuable ceramics, where elements low in the periodic table are important for differentiation purposes, has previously presented a problem. By using the ‘Isoprobe’such measurements are possible. In this instance the separation of early Chinese porcelains into Northern and Southern production groups is shown to be possible. Although samples have been ground from the wares for comparison with optical emission spectrometry, it is shown that analysis of the unglazed portions of the pots themselves gave similar results.     

CHARACTERIZATION OF PACIFIC NORTHWEST COAST OBSIDIAN BY X-RAY FLUORESCENCE ANALYSIS

Several geological sources of obsidian in the Pacific Northwest have been characterized by means of their trace element concentrations, as measured by X-ray fluorescence analysis. The technique is fast and completely non-destructive, making it well-suited for identifying the sources of obsidian from which artifacts were fabricated.     

ENERGY-DISPERSIVE X-RAY FLUORESCENCE ANALYSIS OF CHINESE PORCELAINS USING Am-241

Americium-241 source was used to investigate elements whose fluorescent X-ray energies are between about 25 and 40 keV. We did not find any correlation between the amount of the elements present and the time of manufacture except for barium, which can therefore be used to detect modern reproductions. This method of detection is both quick and non-destructive.     

QUANTITATIVE RESULTS OF XRF ANALYSIS OF ANCIENT COINS BY MONOCHROMATIC X-RAY EXCITATION

The analysis by XRF applied to old coins is improved by use of monochromatic X-ray excitation of variable energy. In addition the effects of relief and irregular shape are eliminated. A method of absolute quantitative analysis without any reference standard has been set up. Results of the analysis of 52 early Greek and 4 late Roman empire gold coins are reported.     

X-RAY FLUORESCENCE ANALYSIS OF ENGLISH 13th-16th CENTURY PEWTER FLATWARE

Most of the thirty-six pewter items were found to have been made from high quality tin-rich alloys with low lead content, hardened with a small amount (0.5–3.0%) of copper; these were thought to be from the later part of the period. Three items, one with the highest copper content of all the alloys, were thought to be from the earlier part of the period. Five items with up to 2% of copper hardener but with lead levels up to 26.5% were thought to be of provincial origin. A possible correlation of alloy composition and date and place of manufacture with rim-form is discussed. A wavelength-dispersive technique was used for the analyses.     

X-RAY FLUORESCENCE ANALYSIS WITH SYNCHROTRON RADIATION ON THE INKS AND PAPERS OF INCUNABULA

Non-destructive X-ray fluorescence analyses induced by white synchrotron radiation (SYXRF) have been performed on a page of the Gutenberg Bible and 21 other different single leaves printed in the years 1470 to 1500. Absolute elemental areal densities for the papers and the inks are reported. The known high Cu and Pb content in Gutenberg's ink is confirmed. The elemental compositions of the other inks, if measurable by XRF at all, are in general very low, governed only by a few additional elements and found to be not distinctive for a known printer. This will render an identification of the printer or printing offices by ink composition analysis in the period after 1470 difficult.