Dyed blue howlite (turquoise imitation), possibly dyed magnesite

Polished opaque blue cabochon with irregular pale or whitish cloudy veining and a glassy-to-waxy surface luster. Howlite has a Mohs hardness of about 3.5, specific gravity around 2.5–2.6, and a monoclinic crystal structure, although the finished cabochon does not show crystal faces or cleavage. The strong turquoise-blue color is not typical of natural howlite and is usually produced by dyeing. It may also be dyed magnesite, which has similar appearance and properties.

Natural howlite forms as a borate mineral in evaporite-rich hydrothermal deposits, commonly as white, chalky nodules or masses. Magnesite forms in altered ultramafic rocks and sedimentary or hydrothermal environments. These minerals formed at various geological ages, generally much younger than the surrounding host rocks. The specimen shown has been cut, polished, dyed, and set into a metal pendant.

Used mainly for inexpensive jewelry, cabochons, beads, carvings, and decorative objects. Dyed howlite and magnesite are commonly marketed as affordable turquoise substitutes. It is not normally used for construction or industrial purposes in this finished form.

Howlite is naturally white to gray and commonly has dark gray spiderweb-like veining. Bright blue specimens sold as 'turquoise howlite' are generally dyed. Natural turquoise is a hydrated copper-aluminum phosphate, CuAl₆(PO₄)₄(OH)₈·4H₂O, and is chemically unrelated to howlite. Dye may concentrate in surface fractures and porous areas.

The combination of intense, unusually uniform blue color, pale cloudy matrix, and a low-cost polished cabochon setting strongly suggests dyed howlite or dyed magnesite rather than high-grade natural turquoise. Useful checks include a loupe examination for dye concentration in cracks, an inconspicuous acetone swab test for transferable dye, and a hardness test: the material should be scratched by a steel point more readily than turquoise. Avoid destructive testing on the jewelry. A gemological laboratory or refractive-index and spectroscopy testing would be needed for certainty.