Technology and Weathering of Mesoamerican Jades as Guides to Authenticity
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TECHNOLOGY AND WEATHERING OF MESOAMERICAN JADES AS GUIDES TO AUTHENTICITY LEONCIO A. GARZA-VALDES Rosa Verde Tower, 343 W. Houston St. Suite 612,
San Antonio,
TX 78205
INTRODUCTION The beauty of a carved pre-Columbian jade defies description. Unfortunately, thousands of fake jade pieces are in museums and private collections. In the study of authenticity, it is necessary to scientifically analyze the surface, observing the changes produced by reactions with the environment, mostly aqueous soil mixtures. MATERIALS The artifacts used in this research included: (1) 10,121 jade flakes and broken pieces from a Maya lapidary workshop at the site of Guaytan in the Middle Motagua Valley in Guatemala, (2) a surface collection of green rocks made in 1987 in the Middle Motagua Valley, (3) 15 pre-Columbian jade artifacts of unknown proveniance, known as the Ahaw Collection, and (4) five fake jade artifacts of unknown proveniance. Several analytical techniques were used in this study: electron microprobe analysis, energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), optical microscopy (transmitted and reflected light), polarized light microscopy, refractometer, scanning electron microscope (SEM), specific gravity determination, ultraviolet fluorescence (2,537 and 3,654 A.U), X-ray diffraction (XRD), and X-ray fluorescence (XRF). Lapidary Workshop In 1979 and 1980, Walters excavated at the site of Guaytan a pre-Columbian lapidary workshop [1]. Twenty trenches were excavated. The broken and complete jade artifacts recovered were deposited at the Instituto de Antropologia e Historia in Guatemala City. Three radiocarbon dates were determined from Guaytan area four: sample 4-6-11, 1,480 ± 90 B.P.; sample 4-6-15, 1,490 ± 70 B.P.; and sample 4-8-22, 1,560 ± 80 B.P. Middle Motaqua Valley Surface Collection A surface collection of green rocks was made at various streams north of the Rio Motagua between Rio El Cintillo in the town of Estancia de la Virgen (see map) and Rio La Palmilla in Guatemala, that is 13 km. to the east. Some omphacitic jadeitite boulders and some jadeitite boulders with a weight of several tons were found at Rio La Palmilla. The Ahaw Collection Fifteen pre-Columbian jades of unknown proveniance and questionable authenticity were studied to apply the hypothesis that weathering can be used as a guide in assessing authenticity. These jades could have been worn as icons by different Maya kings, in the royal costume as objects of power and rulership insignia. These jades played an essential role in defining the prestige and power of the ruler. "Kingly power is concentrated in regalia, which is more important to royal legitimacy than heredity" [2]. Fake Artifacts The technical and surface analyses in five unknown proveniance modern jade artifacts, are reported and compared with the Ahaw Collection.
Mat. Res. Soc. Symp. Proc. Vol. 185. 01991 Materials Research Society
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INFRARED ABSORPTION SPECTROSCOPY The main analytical tool used in
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