Fake turquoises investigated by Raman microscopy

Turquoise is frequently adulterated by unscrupulous dealers and, not rarely, simulants are commercialized as true stones. On the other hand, turquoise is a cryptocrystalline mineral and its use in adornments commonly demands some kind of treatment to facilitate its manipulation, such as impregnation using oil or fats, consolidation with resin and stabilization or reconstitution made with resins. In this work, Raman microscopy was employed in the investigation of turquoise adornments aiming to differentiate processed turquoise from fakes or simulants. Only one out of the five adornment objects analyzed was truly stabilized turquoise (powdered turquoise aggregated with a resin). Another one was constituted of turquoise, calcium carbonate, phthalocyanine blue and resin; the other objects were dyed minerals.