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| Southwestern North America (D. Rumsey Collection) |
“I am an archaeologist who uses
lead isotope analysis to source the ores used to make glaze paints on pre-contact
and early historic Pueblo glaze painted pottery.”, was the introductory sentence
of an e-mail received by Brad Johnson, Arizona Geological Survey (AZGS) research scientist, on 15 April (tax day) 2017.
Archaeologist
Judith Habicht Mauche, University of California at Santa Cruz, expressed her
interest in expanding her research on lead-glazed paints and pigments of the
Zuni and Pueblo potters of New Mexico to the upper Little Colorado River of
north-central Arizona. In e-mailing Brad, she hoped that AZGS could supply a
suite of lead-rich minerals from Arizona’s metallic mineral districts sampling.
She came to the
right place. For the past year, AZGS staff curated the assets of the Arizona
Mining, Mineral and Natural Resources Museum (MMNRE). Including more than
21,000 mineral specimens from the collection of the former Arizona Mining
and Mineral Museum; ~ 35% of those minerals (~ 8,000 specimens) originated in
Arizona’s metallic mineral districts (Carter and Conway,
2017).
Dr. Habicht
Mauche’s primary interest was in common lead ore minerals galena (PbS) and
cerussite (PbCO3). Mineral curator
Catie Carter scavenged nearly 50 specimens for Dr. Habicht Mauche to sample.
Sampling involves scraping the face of the mineral with a small carving knife
with a disposable blade, changed out after each mineral to avoid contamination.
A minute shower of mineral flakes is captured on paper, which is then folded
and placed in a sealed and numbered plastic envelope for later lead isotope
analysis. (Museum quality galena and cerussite were not provided in the sample
set.)
From about AD 1275 to the 1700s, indigenous people of the
Southwest included lead flakes in glaze and paint pigments. The practice ended
about AD 1680, at the time of the Pueblo Revolt when the Pueblo Indians drove
the Spanish from New Mexico (then the province of Santa Fe de
Nuevo México).
As Juliet explains in the accompanying video, ‘Getting the lead out! Using Pb isotopes to
track Native American lead glaze technology’, lead glazing
and pigment technology originated in the upper Little Colorado River before
migrating east and south into the Rio Grande valley of southern New Mexico.
The lead isotope fingerprint of individual galena and
cerussite ore deposits is unique. So matching isotopes from the mineral source with
lead isotopic signatures of the paints or pigments pinpoints the source area. According
to Dr. Habicht Mauche, by
examining the concentration of lead, copper and manganese, ‘we can see specific paint recipes and we can
see how those specific paint recipes moved from one area to another.’ The
working hypothesis: paint recipes were specific to particular groups of people.
Fingerprinting the source of the lead provides archaeologist with a tool for
tracking technology transfer across the SW U.S. Thereby shedding light
on migration or trade patterns of the Zuni and Pueblo people of the Southwest.
Carter, C.S. and Conway, F.M., 2017, Mineral, Mining
Artifacts, and Physical Assets of the former Arizona Mining and Mineral Museum.
Arizona Geological Survey Open-File Report OFR-17-02 v 1.1, 24 p.
