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Abstract
Money trees are artifacts dating from the Eastern Han dynasty (AD 25–220) which have been excavated from tombs in China. The branches of these trees are constructed of bronze, and contain images of coins along with figures important to Han beliefs. Samples from bronze branches originating from several different trees were studied using optical metallography, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis and Raman microscopy. The majority of the samples were cast of an alloy containing approximately 15–20% tin by weight. Conclusive evidence of selective corrosion of either the copper-rich a phase or the tin-rich δ phase was obtained. Redeposited copper was observed only in branches exhibiting selective corrosion of the δ phase. A small number of the branches were found to be composed of a low-tin alloy, containing less than 5% tin. One of these branches exhibited an interesting layered structure of malachite, CuCO3·Cu(OH)2, and copper(I) sulphide on its outer surface.