Distinguishing natural Tibetan copper-bearing andesine from its diffusion-treated counterparts using advanced analytical methods

Red andesines from different collection points in Tibet have been tested for authenticity. Copper-bearing red andesine from the so-called new mines in Tibet (first reported in 2010) can be discriminated from diffusion-treated counterparts using high-resoution analytical techniques and methods. The geological process of Tibetan andesine formation involved the circulation of suplhur-rich fluids that enriched Cu in the feldspars, producing a characteristic natural chemical signature. The authenticity protocol used in this work is based on elemental fingerprints, isotopic determinations of copper and argon, and thermal and microchemical fluid inclusion analyses. Our measurements for hand-collected materials from the old mines (first reported in 2008) partly confirm them as authentic. Instead, most of the faceted gem quality stones in the market overlap with the chemical fingerprints of diffusion-treated andesines. The authenticity remains undeterminable unless destructive methods can be used for testing.