Mineralogical and compositional analysis of turquoise artifacts linked to prehistoric mines in New Mexico, USA
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Petrography, Electron microprobe analysis, and X-ray diffraction analysis of thirty turquoise samples from four mine locations compared to ten artifact samples demonstrates that major element chemistry of the turquoise mineral group members is a potential indicator of geologic source. Mineralogical heterogeneity of turquoise has historically complicated attempts at determining the geologic source location of cultural artifacts. Mineralogy combined with chemical analysis provides major element ranges for comparison. Overlapping ranges of the cations Cu, Al, and Fe involved in the solid solution series of the minerals turquoise, chalcosiderite, and planerite show promise for providing chemical signatures of turquoise sources. Preliminary results show that samples from an Ancestral Puebloan archaeological site near Thoreau, New Mexico have more compositional similarity to a prehistoric mine at Hachita than geographically closer mines in the Cerrillos mining district.