Raw turquoise, a naturally occurring gemstone, forms within the Earth, often embedded in a host rock. Understanding how to identify genuine raw turquoise is important for collectors, enthusiasts, and anyone considering a purchase, as the market contains numerous imitations and treated materials.
Visual Characteristics of Raw Turquoise
Raw turquoise exhibits a spectrum of colors, from sky blue to greenish-blue and yellowish-green hues. Copper often contributes to bluer shades, while iron impurities create greener tones. Its appearance can be mottled or display dark splotches, reflecting its natural formation. The surface generally possesses a waxy to sub-vitreous luster.
The stone is typically opaque, though very thin pieces might show slight translucence. A defining feature is the “matrix,” remnant minerals of the surrounding host rock naturally interwoven within the gemstone. This matrix can appear as veins or splotches in colors like black, brown, tan, or yellow. Common matrix minerals include limonite, sandstone, chert, quartz, or even metallic pyrite.
Matrix patterns vary significantly, from linear veining to intricate “spiderweb” formations, where fine, web-like seams create distinct designs. The presence and pattern of this matrix are strong indicators of natural raw material. The texture of raw turquoise can also be somewhat rough or granular, reflecting its unrefined state.
Common Materials Mistaken for Turquoise
Many materials are mistaken for raw turquoise, often due to intentional alteration. Dyed howlite is a frequent substitute; this naturally white mineral has gray or black veins that, when dyed blue, can resemble turquoise matrix. Howlite’s veins are often more uniform in thickness or appear with a crackle effect, unlike natural variations in genuine turquoise. Dyed magnesite, a white magnesium carbonate mineral, is another common imitation. It is porous and readily absorbs dyes, often marketed as “Turquenite.”
Plastic and resin are also used to create lightweight imitations. These often lack the density of real stone and may have an unnatural sheen. The “matrix” on plastic fakes might appear painted on rather than naturally integrated. Other natural stones can also be confused with turquoise due to similar coloration. Chrysocolla shares blue and green hues but typically displays a wider range of color variations and is generally softer.
Variscite is another mineral frequently mistaken for green turquoise. While a hydrated aluminum phosphate like turquoise, variscite lacks copper, with its green colors stemming from chromium or vanadium. Variscite tends to be a brighter, more consistent green and often has less complex matrix patterns than turquoise. Dyed jasper, sometimes sold as “African Turquoise Jasper,” can also be treated to resemble turquoise.
Simple Methods for Identification
Identifying raw turquoise often begins with visual inspection. Examine the stone’s color consistency; natural turquoise exhibits subtle variations in hue, whereas imitations may have an unnaturally uniform or overly saturated color. Observe the matrix pattern, if present. Authentic matrix lines are integrated and can often be felt with a fingernail, while painted-on patterns will feel smooth or show obvious brushstrokes. The luster of genuine turquoise is typically waxy to sub-vitreous, so an overly shiny or plastic-like appearance can indicate an imitation.
A “feel” test can also provide clues. Real turquoise feels cool and dense, possessing a noticeable heft for its size. Lighter materials like plastic or resin often feel warmer and less substantial. Genuine turquoise has a specific gravity ranging from 2.6 to 2.9, making it denser than many plastic imitations.
The scratch test, while requiring caution, can differentiate turquoise from softer imitations. Turquoise ranks between 5 and 6 on the Mohs hardness scale. Materials like dyed howlite (Mohs 3.5), magnesite (Mohs 3.5-4.5), chrysocolla (Mohs 2-4), and variscite (Mohs 3.5-4.5) are significantly softer. Gently scratch an inconspicuous area with a harder object, such as a steel pocket knife (Mohs ~5.5). If the stone is easily marked, it is likely an imitation. Alternatively, an acetone test, applying a small amount of nail polish remover to a hidden spot, can detect dyed stones. If color transfers to the cotton swab, the stone has been artificially colored.