Today, original and high-quality turquoise is very hard to come by. Of course, some varieties are marketed as having permanent color and they have generally been combined with polymeric materials. These types of stones do not change color due to their artificial production and are available in any size.
Although oil is considered harmful to this gem, fat (paraffin or liquid plastic materials) gives it a polished look and makes it durable, filling its pores.
In the past, to improve the appearance of this stone, methods of saturating it with colored oils, waxes and colored plastics were used. These substances emit a foul odor when they come into contact with hot metal. Such stones are usually lighter than their original counterparts.
One of the most important ways to distinguish natural turquoise is paying attention to its back, meaning the matrix stone (the stone attached to the back of the turquoise). Neishabour turquoises, which are seen as dark or white turquoises with pyrite, can help us to distinguish.
In the advanced Zachary method, the American turquoises of the Kingman mine are improved, which is only determined by machines, and normally there is no indication as to whether this turquoise has been improved or not! With this method, the strength of turquoise and its resistance to both cutting and chemicals is increased. In Iran, the traditional method is still used.
Stones similar to turquoise
Turquoise is sometimes difficult to detect in nature. For example, in Iran, Variscite stones are very similar to turquoise but with a greenish color. Chrysocola is another mineral that has a similar color but is detectable due to its lower hardness of 2.5 – 3.5. The following table shows some minerals that have similar chemical compositions to turquoise:
Holiate or turquoise substitute
As you can see in the image above, another type of imitation of this gem is made by dyeing usually chalcedony or Holiate. Some people end up thinking that turquoise is white! Holiate veins are like turquoise veins and there are many examples of it in the Iranian market. You can test it with a strong dimethyl solvent and an ear cleaner. Sometimes acetone can not dissolve the paint.
Pressed and synthetic turquoises!
In another example, broken or powdered parts are glued and pressed together or glass, ceramic and plastic are used to repair them. After mixing with resin paint and heating to a temperature above 50 degrees and hardening, the stone is cut. The method of distinguishing them is that they have a synthetic color and are very uniform.
What are the types of turquoise stones?
Turquoises have various colors and designs depending on where they are extracted. In the picture above you can see:
Top row left to right: Greenish-blue turquoise with black background from China, a teardrop shaped, slightly greenish turquoise from Arizona Sleeping Beauty Mine, two sky blue cabochons with chocolate brown background from Altyn-Tyube mines in Kazakhstan.
Center row left to right: A small sky blue turquoise from the Kingman Mines in Arizona and two small, sky blue cabochons from Arizona’s Sleeping Beauty mine.
Bottom row left to right: Two small cabochons with black background from unknown mines in Nevada; A slightly greenish teardrop shaped turquoise on a black and white background from the Newlanders Mine in Nevada and a blue-green rectangular cabochon on a reddish-brown background from a Nevada mine.
The difference between Neishabour turquoise and Kerman turquoise
Kerman turquoise is easily recognizable by the metallic and shiny polish which is due to the presence of pyrite; this is the only difference between turquoise of Kerman and Neishabour and the only way to tell them apart. Of course, Neishabour turquoise generally has white, red or gray streaks instead of pyrite, which are due to its by iron and aluminum rich origins, however there are exceptions.
The difference between Shajar and Ajam Turquoise
Turquoise is divided into Shajari and Ajami types and Iran produces both types. Europeans like the dendritic Shajari type and Iranians prefer the smooth and dendrite-free Ajami turquoise. Ajami turquoise is very popular and its price varies depending on its size, color and weight. The best and most popular color of this beautiful gem is sky blue.
The Shajari type can be found in different hues of blue and green with various types of dendrites. Shajari turquoise is divided into 14 classes based on the type, color and shape of the dendrites. This type is more popular in Europe. This gem is mostly cut as cabochons cuts and faceted and fancy cuts are not common. Unlike the Tibetan type, Iranian turquoises generally have large dendrites. Also, Iranian stones are darker than Tibetan ones.