Instructions for gemologists using Dichroscopes: A guide to proper gemstone analysis
In the world of gemology, a crucial instrument that aids in the identification and analysis of gemstones is the dichroscope. This tool is primarily used to observe a gemstone's optical property known as pleochroism – the ability of a gemstone to show different colours or shades when viewed from different angles.
Doubly refractive gems, which split light into two rays traveling at different speeds and directions inside the crystal, are the ones that exhibit pleochroism. The dichroscope helps gemologists and enthusiasts identify whether a gemstone is singly or doubly refractive and observe pleochroic colours, which is a key diagnostic feature in gemstone identification.
The dichroscope, an accessible and straightforward instrument, allows the viewer to see two colours or shades simultaneously through two adjacent viewing windows. If the gem is doubly refractive and pleochroic, the two colours will be different, helping to confirm this optical characteristic. Conversely, when both windows show the same colour, it indicates that the gemstone is singly refractive (not pleochroic), which narrows down possible gemstone types.
This distinction between singly and doubly refractive gems is a fundamental step in confirming a gem’s identity before more complex analyses (like spectrometry) are performed. The dichroscope is especially useful for distinguishing between certain natural gems and simulants or glass, as many common glass imitations do not show pleochroism.
The traditional dichroscope used in gemology is the one with optical-grade calcite. There are two types of dichroscopes: one with two polarizing filter pieces (London dichroscope), and one with optical-grade calcite. Both types of dichroscopes give a split image, which reveals pleochroic colours.
In conclusion, the dichroscope is an invaluable tool for gemologists and enthusiasts alike, helping to identify and confirm the pleochroic properties of gemstones. By doing so, it aids in the accurate identification and analysis of gemstones, ensuring that each stone's unique characteristics are understood and appreciated.
[1] A dichroscope is a relatively inexpensive instrument used in gemology. [2] The dichroscope can help determine if a doubly refractive gem is uniaxial or biaxial. [3] The dichroscope can help identify if a stone exhibits pleochroism, which confirms that the stone is doubly refractive. [4] Occasionally, a refractometer or polariscope may give ambiguous readings, and the dichroscope can clarify that information. [5] It is often difficult to tell if you’re seeing anomalous double refraction (ADR) in red and purple stones, but the dichroscope can help with this. [6] The dichroscope can help confirm other gemological test results. [7] You can make a dichroscope yourself. [8] The second photo depicts a dichroic gemstone viewed through this tool (Photo © Joel E. Arem, PhD, FGA). [9] Gems with isometric crystal structures do not exhibit pleochroism. [10] Pleochroism is a property exhibited by some gems, where they appear different colours depending on the direction the light is polarized.
[1] In the realm of health and wellness, understanding medical-conditions and their effects on the body is fundamental, much like in gemology, where the dichroscope is crucial for identifying and analyzing gemstones.
[2] Similarly, technology plays a pivotal role in modern science, just as the dichroscope, an accessible and straightforward instrument, aids gemologists and enthusiasts in their investigations, revealing the pleochroic properties of certain gemstones.
