Peridot Identification Guide
In the colorful world of gemstones, peridot stands out with its fresh and natural color. It is as green as spring leaves and full of vigorous vitality, which is deeply favored by everyone. Today, we will reveal the identification skills of peridot to you in depth, so that you can accurately distinguish its authenticity and quality when facing it.
- I. Identify the quality by color
High-quality peridot usually has a medium to rich yellow-green color, with a uniform and harmonious tone and no obvious color bands. However, due to different iron content, its color will vary. The higher the iron content, the darker the color, and it is possible to transition from olive green to green-brown. Pure yellow-green is the ideal color of peridot.
For example, the peridot in Figure 1 shows a rich and uniform yellow-green color without any impurities. This is the typical color of high-quality peridot. The peridot in Figure 2 is slightly dull in color and has a slight brown tint, indicating that its iron content is relatively high and its quality is slightly inferior.
Figure 1 High-quality peridot
Figure 2 Dark peridot
- II. Luster and transparency
Peridot has a glassy luster. When illuminated by light, it reflects brightly and softly, like a fine glass product. It has a high degree of transparency, generally in a transparent to translucent state. Objects behind it can be vaguely seen through it, perfectly demonstrating its luster and transparency characteristics.
III. Hardness test
The Mohs hardness of peridot is between 6.5 and 7, which is relatively hard. You can try to use it to gently scratch the surface of some objects with lower hardness, such as gypsum (Mohs hardness 2) and calcite (Mohs hardness 3). If peridot can leave scratches on the surface of these objects without any damage to itself, it means that its hardness meets the characteristics of peridot. However, it should be noted that this test method is destructive to a certain extent, so it must be used with caution in actual identification.
IV Professional Instrument Identification and Analysis
(I) Magnification for gemstone observation
Using a magnifier or microscope to observe the interior of peridot, some unique inclusions can often be found. Among them, the “lily pad”-shaped inclusion is one of the typical characteristics of peridot. This type of inclusion usually has a solid crystal inclusion or negative crystal as the core, surrounded by disc-shaped stress cracks or gas-liquid inclusions, which looks like a lotus leaf floating on the water. In addition, crystal inclusions such as chromite and chrome spinel may also be observed.
Figure 3 is a photo of peridot inclusions taken under a microscope, which clearly shows the morphology of the “lily pad”-shaped inclusions, providing a strong basis for identification.
Figure 3: Lily pad-shaped inclusions in peridot
(II) Accurate determination by gem refractometer
The refractive index of peridot is between 1.654 and 1.690, and the birefringence is 0.036. The refractive index value can be accurately measured by using a gem refractometer, and compared with the standard value to determine whether it is peridot.
(III) The mystery under the polariscope
Put the peridot under the polariscope and rotate the gemstone once. It will appear in four times “bright” and four times “dark”. This indicates that it is an inhomogeneous body, which is consistent with the optical properties of peridot.
(IV) Spectroscope to Insight into Iron Spectrum
Peridot can be observed in iron spectrum under a spectroscope. There are three clear absorption bands at 493nm, 473nm and 453nm in the green-blue region. Based on these absorption bands, peridot can also be identified.
You can choose the identification instrument that suits you according to your budget. Once you master these peridot identification methods, you can accurately select the peridot of your choice and quality in the complex and ever-changing gem market. Whether it is for collection or wearing, a real peridot will add unique charm and value to you.