Page 262 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

F I G U R E 7. 3 Scanning
electron photomicrograph
showing the morphology
of sampleite on a Moche-
style spider nose orna­
ment from ancient Peru
(magnification χ 1145) .
Collections of The Metro­
politan Museum of Art,
New York (1979.206.1230) .

FIGURE 7.3 is a scanning electron photomicrograph of sampleite on an ancient Peruvian
nose ornament of gilded copper from Loma Negra in the collections of the Metropolitan
Museum of Art. The surface of the ornament had been disfigured by several types of corrosion
that included a blue-green sampleite layer over gilded surfaces on a silver-copper alloy back-
plate. The sampleite was confirmed by SEM-EDAX, which determined the presence of copper,
calcium, sodium, chlorine, and phosphorus. The photomicrograph, taken by Howe (1994),
reveals a morphology of closed buds with multiple petal-like crystal components. This morphol­
ogy is more often associated with synthetic copper minerals, such as the copper acetate-arsenite
pigment emerald green.
Sampleite's association with arid environments has also been confirmed by the mineral's
discovery on ancient Peruvian objects made of copper alloys. The burial environment of these
artifacts is analogous to that of Egyptian bronzes; it is extremely arid and subject to periodic
wetting, resulting in groundwater solutions of unusual composition. In addition to Howe's
identification of sampleite on Peruvian objects, the author identified sampleite on a copper alloy
mask from the Moche civilization of Peru that dated to around the second century C E . and that
can be assumed to be from an arid environment (Scott 1994b). Sampleite was also identified
from a Moche face mask in the collections of the Santa Barbara Museum of Art (PLATE 47). The
mask was inlaid with bone eyes and with pupils of an iron-rich mineral that, surprisingly, could
not be identified. The sampleite is mixed with malachite and cuprite within the patina.
Some evidence suggests that sampleite may form from alteration of other copper minerals.
Angelini and coworkers (1990) identified sampleite from a green pigment cake found in Egypt
during the 1903-5 Italian Archaeological Mission excavations of Heliopolis. The exact date of
these finds in not known but could possibly be from the Nineteeth to the Twenty-sixth Dynasty,
which dates the material to between the eighth and the seventh centuries B.C.E.

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