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Gold, gildings, and tumbaga from the Moche tomb of the Lady of Cao: An EDXRF test for the internal ratio method
Author(s) -
Cesareo Roberto
Publication year - 2019
Publication title -
x‐ray spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.447
H-Index - 45
eISSN - 1097-4539
pISSN - 0049-8246
DOI - 10.1002/xrs.3021
Subject(s) - gilded age , copper , necklace , materials science , art , archaeology , mineralogy , metallurgy , chemistry , history , mathematics , combinatorics , keynesian economics , economics
Gold, gilded copper, gilded silver, and tumbaga artifacts from the Moche tomb of the Lady of Cao, dated around 300 A.D., were analyzed by energy‐dispersive X‐ray fluorescence analysis. These artifacts are multilayered structures, which can be “reconstructed” using the K or L rays ratio of the chemical elements present in the layers. For example, in the case of gilded copper, the ratios Au (Lα/Lß), Cu (Kα/Kß), and Au‐Lα/Cu‐Kα, altered with respect to bulk gold or copper, can be used to determine the gilding thickness. An ideal test of this method was recently offered by the study of 15 big spears on gilded copper, a necklace composed of 12 small heads on tumbaga (a poor gold‐alloy subject to depletion gilding), and a nose decoration on gilded silver. All these artifacts were found in (or close to) the tomb of the Lady of Cao, discovered 10 years ago in the north of Peru, close to Trujillo. The “internal ratio” method is described and discussed.