How do you know if turquoise is real?

Believe it or not, fake turquoise accounts for about 90% of the turquoise the world encounters on a daily basis. This is madness! So what can you do to make sure the turquoise you buy isn’t fake? There are actually several ways to determine if turquoise is real, and that’s what we’ll cover in this article.

What is fake turquoise

If you want to understand the difference between fake and real turquoise, then first you should know what fake turquoise is.

Fake turquoise is actually an absorbent white mineral called howlite (howlite). And this super absorbent howlite mineral can be dyed almost any color imaginable. And when it’s done correctly, it can be very difficult to tell whether the stone you’re looking at is real or fake.

How to tell if turquoise is real

But fear not, there are a few things that will help you determine whether you are buying dyed howlite or real turquoise. Here are three things you can check:

Price

You’ve heard that if something is too good to be true, it probably is. The same can be said about turquoise and turquoise jewelry. If you come across a turquoise stone for next to nothing or a bracelet or necklace with turquoise that can be bought cheaply, then most likely you have fake turquoise.

Appearance

Another thing you can look for to determine if turquoise is fake or real is a nail test.

Nail test

This method can be used if you have untreated natural stone. Simply run your fingernail across the surface of the turquoise stone. If your nail catches where the turquoise meets the matrix, then chances are it is a natural turquoise stone.

Scratch test

The scratch test will help you determine the hardness of the sample. Howlite is softer than turquoise, so we can use this to our advantage when determining whether turquoise is fake. Just see if the stone scratches easily. If it scratches easily, then most likely it is howlit. If the stone is difficult to scratch, then the chances that it is real turquoise increase.

Color

The incredible color that turquoise is famous for comes from a mixture of several different natural ingredients. The main contribution to the blue color of turquoise comes from the copper contained in the stone. When it combines with water, aluminum and phosphorus, turquoise is obtained. Of course, this is a simplified version of events, but you get the idea. But it should be remembered that the difference in the amount of any of these elements will change the color of turquoise. This is why it is so difficult to find turquoise in nature that is perfectly uniform and evenly distributed in color. Therefore, if you suspect that you have howlite rather than turquoise, try a nail polish test.

Nail polish remover test

A word of caution on this. The method we are about to share with you may damage the stone if it is indeed a colored howlite. For this fake turquoise test, you will need nail polish remover and a cotton ball or tissue. On an inconspicuous area, such as the back or side of a stone, simply apply some nail polish remover (acetone) using a cotton ball or tissue. If it is colored howlite, then the blue color will be visible on the cotton ball.

Conclusion

We hope these tips on how to tell if a particular turquoise stone is fake will help you in doing so. Remember, if it’s too good to be true, it probably is. If the turquoise is unnaturally uniform in shape and color, then it is most likely a fake. And if the stone is easily scratched or the blue paint can be rubbed off, then it is fake turquoise. Turquoise has long been considered one of the most easily imitated stones. All kinds of imitations make up more than 80% (!) of the modern turquoise market. Already in the Middle Ages, people learned to refine low-quality natural turquoise using wax impregnation; Today, along with this, coloring of stones is also used. In addition to imitations and refined stones, the market situation is complicated by the presence of synthetic turquoise. Rice. 1. Brooch with turquoise and diamonds. Photo: Sotheby’s Thus, the problem of gemological identification of turquoise turned out to be very relevant. Of course, an experienced gemologist will, in many cases, accurately name the deposit of turquoise, the method of synthesis and refining of the stone. But even he sometimes faces the need to conduct special instrumental studies. The problem of identifying turquoise, its imitations and refining was solved at the Gemological Center of Moscow State University using two methods – optical and Raman spectroscopy. Composition, color, properties Turquoise is a hydrous phosphate of aluminum and copper. As a rule, turquoise contains microinclusions of other mineral phases – quartz, chalcedony, opal, carbonates, sulfides and clay minerals. The presence of the latter leads to a deterioration in the color of turquoise and makes it difficult to polish. The color of turquoise – its main advantage – varies greatly, varying from bright bluish blue, sky blue and greenish blue to pale blue. The sky-blue color is due to copper, the greenish tints are due to impurities of iron oxide. The color of turquoise is often spotted, with black or brown streaks. In the latter case, turquoise acquires a mesh or cobweb structure (“network turquoise”). Jewelry varieties of turquoise are characterized by a waxy luster, and after polishing they acquire a strong glass luster. The average refractive index of massive turquoise varieties is 1,62. The hardness of the best jewelry samples on the Mohs scale is 5-6 (in kaolinized varieties it decreases to 3-4). Density ranges from 2,8 g/cm 3 for unaltered samples to 2,5-2,6 g/cm 3 for weathered varieties. Turquoise is characterized by microporosity, which increases sharply with weathering. To a large extent, it is susceptible to the action of various household substances – perfumes, oils, fats, chemical compounds, especially organic ones (gasoline, acetone). Turquoise deposits Turquoise deposits tend to occur in regions with arid climates. The best turquoise in the world is mined from deposits in northern Iran, the USA (Arizona), Mexico and the Sinai Peninsula. The deposits of Mongolia, Afghanistan, China, Israel, Kazakhstan, and Uzbekistan are also considered rich. Turquoise-bearing areas are rocky deserts with mountain ranges or dissected mountain ranges. The most ancient mines are considered to be the Nishapur deposits of Iran, deposits of Mexico and America. The development of these deposits lasted for 7-10 thousand years. It is amazing that these same areas continue to be suppliers of turquoise to this day. Rice. 2. Samples of turquoise from various deposits, from left to right – Biryuzakan (Tajikistan), Dolinnoye (Uzbekistan), China, Akturpak (Uzbekistan), Tibet Rice. 3. Samples of turquoise from Mongolia (left) and Armenia, Tekhut deposit (right) Imitation turquoise The persistent demand for turquoise and the shortage of natural raw materials have led to an abundance of its imitations. Turquoise is often counterfeited with plastic, which melts when heated and smells bad. It is easily distinguished from turquoise by its much lower hardness and density. Fakes made by surface painting of special ceramics, porcelain, glass, bone, quartz (or chalcedony) are common. The so-called “Viennese turquoise” is marketed as turquoise – a heat-treated and pressed thin mixture of malachite with aluminum hydroxide and phosphoric acid. Since 1957, under the name “Neolithic”, a pleasant blue stone has been offered, which is a mixture of copper phosphate and aluminum hydroxide (bayerite), a by-product of aluminum production. Most imitations have a bright and uniform color, which is not typical for natural turquoise. Often in these samples one can observe a more saturated color along the cracks, which is the result of staining. When imitation turquoise is heated, it usually blackens or fuses into black glass rather than cracking like turquoise. Some minerals have similar color and physical properties to turquoise and are used as its analogues. Examples include chrysocolla, variscite, amazonite, and lapis lazuli. An unusual imitation of turquoise is odontolite, which is the bone remains of mammals and fish, partially replaced by the mineral vivianite, which gives the odontolite its blue color. Recently widespread imitations of turquoise are “composites”, the basis of which is carbonates (magnesite, dolomite, calcite), ground into powder and glued with plastic or epoxy resin. The color of these minerals is white, so they are used after dyeing. For the same purposes, turquoise of very poor quality is sometimes used. These types of imitations—made from both turquoise and other minerals—are often referred to in the marketplace as “reconstructed” or “restored” turquoise. The distribution of the dye may be uneven, and the color is often more intense than that of turquoise. Rice. 4. Imitations of turquoise, from left to right – plastic, unknown material, painted magnesite, unknown material Rice. 5. Beads made of dyed magnesite (imitation turquoise) Refinement of natural turquoise The abundance of low-grade raw materials at each deposit necessitates its upgrading, which dramatically increases the profitability of deposit development. The simplest and oldest method of refining is impregnation of turquoise with paraffin or wax. Currently, resin, plastic or sodium silicate impregnation technologies are used. This treatment allows you to reduce the porosity of turquoise and enhance the color, as well as protect it from further changes. With high-quality processing, refined turquoise is visually indistinguishable from high-grade natural samples. As mentioned above, reconstructed turquoise is found on the market. It is obtained by cementation of crushed low-grade natural turquoise. Accurate diagnosis of such samples can only be carried out in the laboratory. Less commonly used is painting the veins in turquoise, as well as filling cavities on the surface with epoxy resin. This refining improves the surface of the stone, and metal fragments added to the resin imitate pyrite inclusions. Rice. 6. Turquoise from US deposits (on the right are samples from Arizona). Turquoise painted Synthetic turquoise Currently, there is also synthetic turquoise on the market, which is quite similar in composition to natural turquoise. In products, synthetic turquoise is almost indistinguishable from natural turquoise, since its basic physical properties are identical to natural varieties. The first synthesis of turquoise took place in 1927 in Germany. In Russia, at VNIISIMS (All-Russian Research Institute for the Synthesis of Mineral Raw Materials), in addition to homogeneous turquoise of various shades of blue, mesh or spider turquoise was also artificially obtained, imitating the best natural samples. It is difficult to distinguish synthetic turquoise from natural turquoise in products; often such stones can only be determined in a laboratory. Optical spectroscopy Optical spectroscopy is a traditional gemological method for studying the nature of color. The spectrum shows how much light is transmitted or absorbed by the sample. The human eye perceives color in general, but does not see specific stripes and lines that appear in the spectrum and are associated with the presence of impurities in the stone. For example, turquoise is colored with copper, which leads to the appearance of broad absorption bands with maxima at 671 and 769 nm. Also, an iron impurity can produce narrow lines in the spectrum of turquoise at 420 and 429 nm. Comparing the spectrum of natural turquoise and its imitations (Fig. 7), we see that they differ significantly. Imitations are characterized by transmission in the range of 800-1000 nm, while this is not typical for natural turquoise. But it is impossible to distinguish natural and synthetic turquoise using this method due to the similarity in the nature of the color. Therefore, Raman spectroscopy must be used to identify natural and synthetic turquoise. Rice. 7. Optical spectra of natural turquoise and colored magnesite Raman spectroscopy A Raman spectrometer measures the spectrum of a mineral that is hit by laser light. These spectral lines correspond to certain vibrations of groups of atoms and make it possible to determine the structure of a substance. In relation to our task, this means that with the help of Raman spectroscopy it is possible to distinguish any imitations, synthetics and detect filler in the turquoise itself. Differences in chemical composition between natural and synthetic turquoise lead to significant differences in their Raman spectrum (Fig. 8). Thus, based on the totality of Raman lines, natural turquoise is easily distinguished from synthetic turquoise. When studying filled turquoise, it was discovered that in the spectrum of such turquoise the lines of both the turquoise itself and the filler simultaneously appear. The specific type of filler (organic substance) cannot always be determined, but its presence is easily determined by spectra. Rice. 8. Raman spectrum of natural (Teghut deposit, Armenia) and synthetic turquoise Conclusions In many cases, identification of turquoise requires the use of instrumental methods available in the laboratory. Using these methods, there are no difficulties in separating natural turquoise from synthetic and refined ones, as well as in identifying the filling of natural turquoise. The Gemological Center of Moscow State University has developed a method for express diagnostics of turquoise, based on Raman and optical spectroscopy. The spectroscopic methods used make it possible to reliably diagnose natural turquoise, as well as recognize imitations, synthetics, and the presence of refining (filling). Material prepared by: R.S. Serov, A.A. Mashkina (Gemological Center, Moscow State University)