Analysis of Gemstones and Diamonds in Jewelry with the FTIR Microscope LUMOS II

Importance of the Topic

The ability to distinguish natural, synthetic and treated gemstones carries significant economic and scientific value in gemology and jewelry appraisal. High-resolution infrared analysis enables non-destructive identification of crystal lattice features and trace impurities, ensuring authenticity and quality control of precious stones.

Objectives and Study Overview

This study, documented in Application Note AN M121, demonstrates the capabilities of the LUMOS II FTIR microscope for in situ analysis of mounted diamonds and colored gemstones in jewelry. The aim is to show how fully automated FTIR microscopy overcomes spatial resolution challenges posed by small or closely packed stones, including sunk-in settings.

Methodology and Instrumentation

Samples were examined without removal from their settings using a high-working-distance microscope equipped with automated optics and a tilting sample vice. Measurement points are positioned via a video-wizard guided workflow, optimizing sensitivity while maintaining ease of use for non-experts.

Used Instrumentation

• LUMOS II FTIR microscope
• OPUS software with video-wizard interface
• Special sample holder vice for jewelry mounting and tilting

Main Results and Discussion

Diamond analysis of a mounted ring revealed sharp two-phonon bands between 1,600–2,700 cm⁻¹ and nitrogen-related absorptions at 500–1,500 cm⁻¹, identifying the stones as natural type IaA and type IaAB diamonds. Organic C–H stretching bands below 3,000 cm⁻¹ indicated surface contamination from skin oils.

In a gold ring containing colorless, blue, red and green stones, FTIR spectra classified the blue and red gems as corundum varieties (sapphire and ruby) via characteristic reflection bands. The green stone exhibited beryl signatures, confirming its identification as emerald.

Benefits and Practical Applications

The presented approach offers:

• Non-destructive, high-selectivity identification of individual stones within complex settings
• Reliable differentiation between natural, synthetic and treated gemstones
• Rapid routine operation by non-specialists without compromising sensitivity

Future Trends and Opportunities

Advancements may include integration of hyperspectral imaging, AI-driven spectral interpretation and miniaturized probes for enhanced on-site gemological surveys. Further development could broaden applications to archaeological artifacts and high-throughput industrial gem screening.

Conclusion

The LUMOS II FTIR microscope, combined with intuitive software and specialized sample handling, enables precise, non-destructive analysis of mounted diamonds and gemstones. It delivers critical information on stone origin, treatment history and composition, supporting quality assurance in gemology and jewelry industries.

Reference

• Bruker Optics. Application Note AN M121: Analysis of Gemstones and Diamonds in Jewelry with the FTIR Microscope LUMOS II, 2021.