How to Identify Raw Turquoise

Turquoise is a valuable gemstone that has been used for jewelry and decorative purposes for centuries. It is a blue-green mineral that is typically found in arid regions, and its distinctive coloration and texture make it a popular choice for jewelry designers. However, identifying raw turquoise can be challenging, as there are many different types of stones that may be mistaken for turquoise. In this article, we will discuss the main characteristics of raw turquoise and the methods that can be used to identify it.

What is Turquoise?

Turquoise is a copper-containing mineral that is typically found in arid regions. It is a hydrated phosphate of copper and aluminum, with the chemical formula CuAl6(PO4)4(OH)8·4H2O. Turquoise is typically blue-green in color, but it can range from sky blue to a deep green, depending on the presence of different minerals.

Visual Inspection

The first step in identifying raw turquoise is to conduct a visual inspection. Raw turquoise is typically opaque or slightly translucent, with a waxy or vitreous luster. It is typically blue-green in color, but it may also have veins or streaks of other colors, such as brown or yellow. The texture of turquoise is typically smooth, and it may have small pits or cavities on the surface.

Hardness and Scratch Test

Turquoise has a hardness of 5 to 6 on the Mohs scale, which means that it is relatively soft and can be scratched by harder materials. A simple scratch test can be used to determine if a stone is turquoise. Take a piece of glass or a steel file and scratch the surface of the stone. If the stone scratches easily, it is likely not turquoise.

Specific Gravity

Turquoise has a specific gravity of around 2.6 to 2.8, which means that it is relatively lightweight compared to other minerals. This property can be used to distinguish turquoise from other stones that may resemble it. To test the specific gravity of a stone, you will need a scale that can measure weights up to several hundred grams and a graduated cylinder filled with water. Weigh the stone, and then place it in the water-filled cylinder. The displacement of water will give you the stone’s volume, which can be used to calculate its specific gravity.

Magnification

Turquoise may have distinctive inclusions or patterns that can be seen under magnification. Using a jeweler’s loupe or microscope, examine the stone for small veins or spiderweb-like patterns. These are common features of raw turquoise and can help to distinguish it from other stones.

Chemical Tests

Chemical tests can be used to determine if a stone is turquoise. One common test involves using a dropper to place a drop of dilute hydrochloric acid (HCl) on the stone’s surface. If the stone is turquoise, it will fizz and produce bubbles. However, this test should be used with caution, as it can damage the stone if it is not turquoise.

Conclusion

Identifying raw turquoise can be challenging, as there are many different types of stones that may resemble it. Visual inspection, hardness and scratch tests, specific gravity, magnification, and chemical tests are all important tools that can help to identify turquoise. If you believe you have found a piece of raw turquoise, it is important to handle it with care and seek the advice of a professional gemologist or mineralogist.