gems, turquoise, turquoise identification, turquoise imitation, dyed magnesite

Magnesite dyed blue to imitate turquoise has appeared on the market, including necklaces made from tumbled nodules sourced from Africa. This imitation can be identified by spot refractive index readings of 1.51 and 1.70, with the high birefringence indicating a carbonate. Its specific gravity, around 3.0, is higher than that of calcite or dolomite, both commonly used as turquoise simulants. Once identified as magnesite, the artificial nature of the coloration becomes clear, as blue magnesite does not occur in nature. Additionally, the recessed matrix areas in these nodules are filled with a wax-based black substance—likely added during polishing—to mimic the appearance of spiderweb turquoise.