TLDR
Ancient jade from Jinsha changed color because substances from nearby bronze objects settled onto it. Careful light-based testing can identify these changes without damaging the artifacts and can reveal harmful substances.
Summary
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1 Study Aim
The study aimed to identify the materials causing six color alterations (chemical or structural changes) on ancient jade from the Jinsha Site. The authors also investigated whether these changes came from nearby bronze corrosion and whether nondestructive testing could reveal other substances important for conservation and researcher safety. The researchers wanted to explain the jade’s unusual colors without harming these rare objects.
2 Study Design
The research examined 14 nephrite jade fragments from the Meiyuan sacrificial area of the Jinsha Site. Raman spectroscopy (a light-based method for identifying minerals) analyzed their mineral phases. Optical microscopy examined surface structures, while scanning electron microscopy with energy-dispersive spectroscopy (SEM–EDS, imaging combined with chemical analysis) examined microstructures and elemental composition. The study used 633- and 785-nanometer lasers at room temperature. Jade fragment JS-9 was excluded. The researchers examined many preserved jade pieces using gentle imaging and chemical tests.
3 Findings
The authors identified the jade as nephrite, mainly the mineral tremolite. They linked green, black, yellow, blue, purple, and white alterations to malachite, tenorite, pyromorphite, azurite, diaboleite, and cassiterite. These materials are corrosion products (substances formed when metals break down) from nearby bronze objects. Raman spectroscopy also detected arsenolite, a highly poisonous substance, and organic matter on the jade. The authors recommend protective equipment and lower-energy testing because these materials may threaten researchers or damage artifacts. The colors came from nearby metal decay, and testing found both a poisonous substance and material from the burial surroundings.