Raised relief on nephrite jade artifacts: observations, explanations and implications

Add time:08/08/2019    Source:sciencedirect.com

Mineralogical analyses of nephrite jade artifacts have been used to identify likely causes of alterations in which some specimens exhibit raised relief above the original polished surfaces. In all of the specimens examined, the raised areas consist of either large diopside ± large tremolite crystals, or, in a few cases, only fibrous tremolite, within a non-raised matrix of nephrite (fibrous tremolite). Apparent relief may be cause by a number of different effects, either mechanical (abrasive), chemical (e.g., dissolution), or a combination (mineralogical alteration leading to formation of relief). The most enigmatic examples occur where the relief formed after the object was polished and can not be easily attributed to chemical dissolution or mechanical abrasion. One possible explanation for these is that minor amounts of secondary growth of hydrous minerals, such as clays along grain boundaries, produced a volume increase which caused the crystals to rise. Carbon-14 analysis on one vessel that displays raised relief has produced an age of 3010 ± 30 years before present for organic material that coated the alteration.

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