Analysis of Precious Stones by EDX-8100

Significance of the Topic

Determining whether gemstones are natural or synthetic and identifying their geographic origin are critical tasks in gemology, jewelry appraisal, and quality control. Non-destructive, rapid techniques that reveal elemental composition help authenticate valuable stones, detect treatments such as lead glass filling or color enhancements, and establish provenance for pricing and certification.

Objectives and Study Overview

This study employed energy dispersive X-ray fluorescence (EDXRF) using the Shimadzu EDX-8100 to analyze common gemstones (rubies, emeralds, and Paraiba tourmaline). The goals were:

• Differentiate natural versus synthetic stones based on trace and major element profiles.
• Determine the geographic origin of natural stones through characteristic elemental signatures.

Methodology and Used Instrumentation

Gemstone samples were irradiated directly under vacuum with a 3 mm beam. Qualitative and quantitative analyses covered elements from sodium (Na) to uranium (U) using an SDD detector and Rh target X-ray tube. Tube voltages varied (15 kV for light elements, 50 kV for heavier elements), and multiple primary filters were switched automatically to optimize detection. Measurement time was 50 s per channel.

Additional tools referenced include:

• FT-IR for detecting heat or resin treatments.
• UV-Vis spectroscopy for color treatments.
• LA-ICP-MS for detailed trace analysis of tourmaline.
• OLS5000 3D laser microscope for imaging internal features.

Main Results and Discussion

Rubies:
The natural Tanzanian ruby contained gallium and lower chromium compared with the synthetic counterpart, which showed elevated chromium and zirconium but no detectable gallium—markers distinguishing authenticity.

Emeralds:
Natural Colombian and Zambian emeralds displayed distinct element patterns: Zambian stones had higher chromium, iron, sodium, magnesium, potassium, rubidium, and cesium relative to Colombian samples. Synthetic emeralds contained rhodium from catalysts and lacked sodium/magnesium, allowing clear identification.

Paraiba Tourmaline:
Both rough and cut Brazilian tourmalines showed characteristic copper (> 0.6 wt% as CuO) and manganese contents, confirming natural Brazilian origin. Although manganese varied (0.5 wt% in rough vs. 4 wt% in cut), visual inspection under 3D microscopy revealed internal green zones correlating with higher Mn, despite similar neon-blue hues.

Benefits and Practical Applications of the Method

• Non-destructive, rapid compositional screening of gemstones.
• Reliable discrimination between natural and synthetic gems based on element markers.
• Provenance determination aiding valuation and certification.
• Support for multi-instrument appraisal workflows combining EDXRF with spectroscopic and mass spectrometric methods.

Future Trends and Possibilities for Use

Integration of EDXRF with advanced imaging and laser ablation techniques will enhance spatial resolution of elemental maps. Development of comprehensive databases of gem signatures from global deposits will refine origin assignments. Machine learning applied to combined spectral datasets promises automated, high-throughput gemstone authentication and grading.

Conclusion

The Shimadzu EDX-8100 effectively distinguishes natural from synthetic gemstones and pinpoints geographic origin based on trace and major element analysis. When combined with FT-IR, UV-Vis, LA-ICP-MS, and microscopic imaging, it forms a robust, non-destructive toolkit for gemological research and commercial appraisal.

References

1. Ahmadjan Abduriyim: The Science of Gemstones, ARK PUBLISHING INC.
2. Abduriyim A., Kitawaki H., Furuya M., Schwarz D.: “Paraiba”-Type Copper Bearing Tourmaline from Brazil, Nigeria, and Mozambique: Chemical Fingerprinting by LA-ICP-MS.
3. Abduriyim A., Kitawaki H.: Applications of Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) to Gemology.