Page 271 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

chrysocolla: ICDD 27-I88 and ICDD 11-322. There is also an entry in the mineral reference data-
base by Nickel and Nichols (1991) that is similar to ICDD 11-322 but with some of the higher
d-spacings absent. APPENDIX D, TABLE 9, compares X-ray diffraction data for a chrysocolla
sample from the Old Dominion fault vein in Globe, Arizona, with the three reference data sets.
Data for a second sample, a green pigment from a first-century rock-cut tomb painting at La
Miña, Peru, are also given in TABLE 9. The data are similar to that for ICDD 11-322 (Scott 1997b).
Superseded ICDD files should not be neglected when attempting to match diffraction data for
poorly crystalline pigments such as chrysocolla. 2
Theophrastus and Pliny wrote of the mineral chrysocolla, although there is always the pos-
sibility that they confused it with other copper minerals, such as malachite; it is not always clear
which mineral is being referred to in most of the ancient texts. Chrysocolla achieved importance
in antiquity as one of the copper compounds useful in the reaction soldering of gold.
The reaction soldering process is sometimes referred to as "colloidal hard soldering" or
as the "Littledale" soldering process. The solder, used mainly for gold alloys, is made from a
copper salt and glue. After careful heating with a blowpipe, the copper silicate or other salt
decomposes to cuprite and then to tenorite. The glue reduces the tenorite to copper in situ as it
carbonizes at about 600 - 800 °C. Finally, the copper metal diffuses into the gold, creating a very
neat join without the need to flood the region to be joined with solder. This method is widely
thought to have been used by the Etruscan and Greek civilizations and then rediscovered in the
early twentieth century by Willoughby A. Littledale, an English jeweler.
Moorey (1994) explored the problem of identifying which so-called greenstones were actu-
ally used in ancient Mesopotamia by examining samples from the mesolithic Levant culture
with its type site at Wadi an-Natuf in Israel. He reported that "greenstone" is a general term for
minerals that include malachite, chrysocolla, rosasite, and turquoise. This suite of copper min-
erals is particularly associated with the copper-bearing rocks in the Wadi Feinan of Jordan, the
Timna area of Israel, and in Turkey. Many Mesopotamian artifacts are mineralogically misiden-
tified as jade; for example, a "jade" bead found at the important cave site of Shanidar in ancient
Mesopotamia is actually chrysocolla (Moorey 1994).

Chrysocolla as a pigment When chrysocolla was used as a pigment, the color selected var-
ied from green to turquoise blue. Gettens and Stout (i966) iden-
tified the pigment on tenth-century wall paintings at Kizil in Chinese Turkestan, and Spurrell
(i895) found it in wall paintings from Twelfth Dynasty tombs (1991-1783 B.C.E.) at El Bersha
and at Kahun in Egypt.
The pigment was used sporadically, depending on availability, and by the sixteenth century,
it was given the appellation of Ceder green (Harley 1970). During that time, Agrícola ([i546] 1955)
described a method for extracting chrysocolla for pigment use from deposits in mountainous
areas by first grinding the mineral in place and then transporting it in a series of sluices. Chryso-

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