Testing Gemstone Origin: A Geological Exploration

1. Identifying Internal Characteristics and Locations:

Geological studies of gemstone deposits can be significantly enhanced by examining internal characteristics through tools like microscopes or magnification loops. By carefully studying the inclusions (internal features), we can uncover crucial information about the type of deposit and the environmental conditions that led to the gemstone’s formation. This process can also reveal whether the gemstone has been subjected to any treatments or enhancements.

2. Color Analysis:

Gemstones, when exposed to different types of light—such as daylight, visible light, and infrared light—show distinct color patterns. These color characteristics can serve as a “signature” of the gemstone’s origin and any treatments it has undergone. Analyzing these colors provides insight into the gemstone’s history and the geological conditions that contributed to its creation.

3. Trace Elemental Chemistry:

Gemstones may contain unique trace elements and mineral combinations that differ depending on their geographical origin. Instruments like Energy Dispersive X-ray Fluorescence (ED-XRF) and Laser-Induced Breakdown Spectroscopy (LIBS) can help identify these trace elements, shedding light on the gemstone’s chemical composition. These tests are useful for determining whether the gemstone originated in a known mining region or if it was subjected to any artificial processes.

4. Compositional Studies:

Although still not widely used, compositional studies of gemstones can provide deeper insights into their geological origin. By examining the overall composition of the gemstone, we can gather information about the environmental conditions under which it formed, such as temperature, pressure, and the presence of specific minerals during crystallization.

5. Raman Spectroscopy:

Raman spectroscopy is a powerful tool for analyzing the molecular structure of gemstones. By examining the crystalline structure at a molecular level, we can determine whether a gemstone is natural or synthetic, as well as identify its precise origin. This technology is particularly useful in distinguishing gemstones from different regions that may share similar visual characteristics.

Raman spectrometer testing a stone in the Carlsbad lab. G&G caption: Figure 1. Confocal Raman spectroscopy, which can be used to identify mineral inclusions in gems submitted to the lab, is one of the advanced analytical methods used in geographic origin research.

Conclusion:

Despite the wide range of advanced testing methods available today — including chemical analysis, spectroscopy, and microscopic examination — accurately determining the exact origin of a gemstone remains a complex challenge. This is largely because many mining regions share overlapping geological conditions that produce gems with remarkably similar physical and chemical traits. For instance, sapphires sourced from Sri Lanka, Madagascar, and Burma (Myanmar) often display comparable hues, inclusions, and trace element compositions. As a result, even experienced gemologists may find it difficult to pinpoint a gemstone’s precise source through visual inspection alone, highlighting the importance of laboratory-based origin determination using advanced analytical instruments.

Impact:

Gemstones found in Sri Lanka are often priced higher than those from other countries, such as Madagascar or Burma, due to the reputation of Sri Lankan stones in the market. However, some buyers may only focus on the gemstone’s appearance—such as color and clarity—without considering its geological background or origin.

In conclusion, while testing gemstone origins can provide valuable insights, it often requires a combination of techniques and further research to reach a definitive conclusion. Even with sophisticated testing methods, the origins of many gemstones remain complex and elusive.