Turquoise, a hydrated copper aluminum phosphate mineral, has been prized for its distinct blue-to-green coloration for thousands of years. The stone’s high value has led to a market saturated with imitations, treatments, and reconstituted materials, making verification necessary to ensure true value, as much jewelry labeled “turquoise” is not the pure, natural mineral. Verification methods range from simple visual inspection to minimally destructive home tests. These tests reveal if a stone is natural, treated, or a complete fake.
Identifying Common Imitations and Treatments
The market features two main categories of non-natural turquoise: simulants, which are entirely different materials, and treated turquoise, which is genuine stone that has been chemically altered. The most common simulants are white minerals like howlite and magnesite, which are easily dyed due to their porous nature. Howlite is naturally white with dark grey veining, and when dyed blue, it is often sold as “Turqurenite.” Another common fake is simply plastic, epoxy, or glass, which is molded and colored to mimic the stone’s appearance.
Stabilization is the most frequent treatment applied to genuine turquoise, estimated to be present in up to 90% of the turquoise jewelry sold globally. This process involves infusing porous, or “chalky,” low-grade turquoise with a clear resin or epoxy under pressure. The resin hardens the soft material, preventing it from crumbling during cutting and improving its color and durability, although the resulting stone is no longer considered natural or untreated.
Reconstituted turquoise involves mixing small fragments and powdered waste from cutting with plastic resin and dye. This mixture is then compressed into solid blocks before being cut into shapes for jewelry, sometimes referred to as “block turquoise.” While it contains actual turquoise powder, the material is predominantly a composite held together by a binding agent. This makes them far less valuable than natural material.
Practical Home Tests for Verification
A simple way to check for surface dyes, which are common on simulants like howlite or magnesite, is the acetone test. Dampen a cotton swab with acetone or nail polish remover and gently rub it against an inconspicuous area of the stone, such as the back or a crevice. If the stone has been dyed, blue color will transfer to the cotton swab, indicating the material is a dyed simulant and not solid turquoise. However, this test may not work on stabilized turquoise, as the resin is often infused deep within the stone.
Visual examination under magnification can reveal signs of treatment or reconstitution. Natural turquoise often exhibits minor color variation and a matrix—the spiderweb-like veining of the host rock—that appears organic and slightly irregular. In contrast, reconstituted material may show tiny, uniform pinprick holes or a grainy texture where the powdered stone and resin mixture are visible. If a matrix pattern appears too perfect, uniform, or looks painted on the stone’s surface, it is often a sign of a manufactured simulant.
The temperature and weight of a piece can also offer clues, particularly when trying to distinguish between natural stone and plastic or glass fakes. Genuine minerals feel cool to the touch and take a noticeable amount of time to warm up when held in the hand. Plastic or resin simulants will feel lighter than a comparably sized stone and warm up almost instantly. For a more definitive, though destructive, test for plastic, a heated sewing needle pressed to an unexposed area will melt the material and produce an odor of burning plastic if it is a fake.
Characteristics of High-Quality Natural Turquoise
The primary indicator of high-quality natural turquoise is its inherent hardness and durability without the need for stabilization. Natural turquoise typically measures between 5 and 6 on the Mohs scale of mineral hardness, making it resistant to minor scratches and chipping. Low-grade, chalky material falls on the softer end of this range, which is why it often requires resin treatment to be usable in jewelry.
Untreated turquoise also possesses a unique characteristic known as patina, meaning its color may change subtly over time. Being a hydrous mineral, the porous natural stone can absorb oils, lotions, or moisture from the environment, causing its blue hue to deepen or shift slightly toward green. Stabilized or dyed stones maintain an artificially consistent color because the resin filler prevents absorption. This means a piece with a perfectly consistent color over many years is likely treated.
The context of the purchase is a strong, non-physical sign of authenticity and quality. Natural, untreated turquoise with a vivid, even color is relatively rare and commands a high price. If a stone is perfectly shaped, uniformly colored, and sold at an extremely low price point, it is almost certainly a dyed simulant or a block of reconstituted material. Reputable dealers will always disclose if a stone has been stabilized or reconstituted, as failure to do so misrepresents the material’s value.