Crossing the Borders: New Methods and Techniques in the Study of Archaeological Materials from the Caribbean

36 / Cooper, Martinón- Torres, and Valcárcel Rojas
gence of social inequality associated with inherited power (Valcárcel Rojas and
Rodríguez Arce 2003, 2005). The catalyst for the development or material manifestation
of this hierarchy was unclear.
Therefore, a comprehensive microanalysis of the metal objects from the cemetery
was conducted to study their composition, manufacture, and origin in order to
help interpret their relative value to the indigenous community that buried them.
Laboratory Methods
An initial study of a sample of the metal objects was carried out in the Centre of
Nuclear Development and Technological Application, part of the Ministry of Science,
Technology, and Environment in Havana, Cuba, by energy- dispersive X- ray
fluorescence ( ED- XRF) surface analyses. The corroded condition and small size
of the metal specimens prevented a full quantitative analysis of the metal compositions;
however, surface analysis indicated ternary gold/ copper/ silver alloys and
zinc- rich copper alloys (Valcárcel Rojas 2002). Subsequently, a more detailed analytical
study of the metal assemblage was carried out at the Wolfson Archaeological
Science Laboratories, Institute of Archaeology UCL, London. These analyses employed
ED- XRF, optical microscopy, and scanning electron microscopy with an attached
energy- dispersive spectrometer ( SEM- EDS).
ED- XRF analyses were performed with a Spectro X- Lab Pro 2000; the objects
analyzed were smaller than the detector window (ø 25 mm), and were placed directly
in the chamber without any preparation. These qualitative analyses of surface
compositions allowed comparison with the ED- XRF results from Cuba, and
also with the bulk compositions of mounted cross sections of specimens examined
with the SEM- EDS.
Examination by optical microscopy involved the use of a standard Wild Heerbrugg
stereoscopic microscope for complete objects, and a Leica DM LM for reflected
light microscopy of metallographic cross sections. These were mounted in
epoxy resin and polished to 1 µm grain size following established procedures (Scott
1991).
SEM- EDS was carried out using a Philips XL30 instrument with an INCA Oxford
spectrometer package. Specimens were observed in secondary electron (SE)
and backscattered electron (BSE) modes, and analyzed using the EDS system. Operating
conditions for data collection were as follows: working distance of 10 mm;
accelerating voltage of 20 kV; spot size of 4.7 to 5.3 (INCA conventional units) and
process time 5, corresponding to a detector dead time of 25–40 percent; and acquisition
time of 75 seconds. Based on previous analyses, the lower confidence limits
for this instrument may be established at 0.3 wt percent, and values below this
limit can be taken as indicative only. Bulk compositions given in this paper are averages
of five measurements taken in areas of ~100 µm2, either on the surface of
You are reading copyrighted material published by the University of Alabama Press.
Any posting, copying, or distributing of this work beyond fair use as defined under U.S. Copyright law is illegal and
injures the author and publisher. For permission to reuse this work, contact the University of Alabama Press.