Andalusite Identification Guide: Uncover the Secrets of a Unique Gemstone
In the colorful world of gemstones, andalusite is like a low-key pearl with unique charm. It has a long history and has played an important role in different cultures. Today, it also attracts the attention of many gem lovers and collectors. However, there are a lot of different andalusites on the market, and mastering identification skills is the key to finding the authentic ones you like. Next, we will take you into the world of andalusite identification and unveil its mysterious veil.
- By appearance and color: Unique color of natural andalusite
Andalusite has various colors, the most common ones are brown, brown-green, yellow-brown, green, pink, purple, etc. The color of natural andalusite is natural and has unique pleochroism. When observed from different angles, it can show different colors (as shown in Figure 1) and is rich in layering. The pleochroism visible to the naked eye is one of the important bases for the identification of andalusite.
Figure 1 Andalusite
- By professional instrument identification
(1) Use a gem refractometer to detect the refractive index of andalusite
The refractive index of andalusite is very stable, which is another important basis for identifying andalusite!
The refractive index of andalusite is: 1.634~1.643 (±0.005), and the birefringence is: 0.007-0.013.
If the refractive index detected meets the above values and the pleochroism is visible to the naked eye, the gem can be judged as andalusite.
- Use a gemstone magnifier or gemstone microscope to magnify and observe the internal and external characteristics of andalusite
When observing the inside of andalusite under a magnifier or microscope, some inclusions can often be found. These inclusions have different shapes, which may be gas-liquid inclusions, mineral inclusions, etc. The inclusions of natural andalusite are distributed naturally and randomly. For example, gas-liquid inclusions may appear as tiny bubbles or irregular liquid forms, and mineral inclusions may be fine particles of other mineral crystals. The inclusions of synthetic andalusite are often distributed more regularly, or there are no inclusions at all, which makes it appear too pure. By observing the characteristics of the inclusions, the authenticity and formation environment of andalusite can be further judged.
Figure 2 Crystal gemstones and mineral inclusions
Figure 3 Tubular inclusion
(3) Observe the pleochroism of andalusite using the calcite dichroscope
The pleochroism of andalusite is related to the body color, which is measured by the calcite dichroscope (Figure 4). Andalusite has a strong trichroism, which is visible to the naked eye.
(4) Use a density balance to test the relative density of andalusite
The density of andalusite is relatively stable, ranging from 3.13 to 3.60, and the actual measured value is usually 3.17.
- By gemstone identification certificates issued by authoritative identification institutions
In gem trading, recognizing the gem identification certificate issued by an authoritative identification institution is like buying a quality insurance for the gem. It is not only an authoritative proof of the quality and value of the gem, but also a strong guarantee for the rights of consumers. How can we distinguish the authenticity of a gem identification certificate?
(1) Check the official website of the institution: Search the official website of the identification institution through the Internet to check the background, qualification certification, business scope and other information of the institution. The official website of the formal and authoritative institution has complete information and is updated in a timely manner. You can check the authenticity of the certificate and related detailed information. If you cannot find the official website or the official website information is simple and vague, you need to be wary of the authenticity of the certificate.
(2) Certificate number verification: Each authoritative identification certificate has a unique number, which can be entered on the institution’s official website for verification. If the query result is consistent with the certificate information, and the certificate format is standardized, the content is detailed, and the anti-counterfeiting mark is clear, the certificate can basically be confirmed to be authentic. If the number query is fruitless or the information does not match, the certificate is very likely to be fake.
(3) Anti-counterfeiting mark identification: Authoritative certificates usually use a variety of anti-counterfeiting technologies, such as laser anti-counterfeiting labels, watermarks, special paper, etc. Observe the certificate carefully, the anti-counterfeiting mark should be clear, fine and difficult to copy. For example, the laser anti-counterfeiting label will show unique patterns and gloss changes at different angles, and the watermark can be seen clearly under light.