Diamond Analysis

Importance of the Topic

Infrared spectroscopy offers a rapid, non-destructive approach for distinguishing natural, synthetic and treated diamonds. This capability is critical for accurate valuation, consumer trust and quality control in gemology and industry.

Objectives and Study Overview

This study presents a modular FT-IR workflow for diamond classification and type determination. It addresses polished and rough stones, mounted gems and high-throughput screening of melee diamonds, enabling reliable identification of imitations, HPHT treatments and synthesis origins.

Methodology

FT-IR spectroscopy measures characteristic vibrational absorptions of carbon lattice and impurity atoms. Nitrogen and boron impurities define diamond types: Type I (measurable nitrogen) subdivided into Ia (aggregated) and Ib (isolated), and Type II (no detectable nitrogen) subdivided into IIa (no boron) and IIb (boron). Four sample presentation modes are used: diffuse reflectance (DRIFT) for loose polished stones, transmission for rough crystals, front reflection for mounted gems and microscope-based reflectance for sub-millimeter melee.

Used Instrumentation

• FT-IR spectrometer ALPHA II with DRIFT module and interchangeable transmission or reflection attachments
• LUMOS II FT-IR microscope with integrated camera and sample stage vice for visual targeting
• High-throughput screening accessory HTS-XT coupled to INVENIO S spectrometer for automated analysis of 96 to 1536 positions

Main Results and Discussion

Polished diamonds are classified in under 30 seconds with an automated PDF report showing spectra and type assignment. Rough stones up to tens of carats are measured in transmission mode. Mounted gems, including tightly clustered melee, are selectively probed by LUMOS II, revealing both lattice absorption bands and organic contamination signatures. The HTS-XT module screens large batches of sub-millimeter diamonds in seconds per sample, distinguishing more than a dozen pure and mixed types and detecting imitations with high confidence.

Benefits and Practical Applications

• Fast screening of loose and mounted diamonds in gemological laboratories and retail settings
• High-throughput quality control for sorting centers and industrial applications
• Automated, user-friendly operation requiring minimal spectroscopic expertise
• Reliable detection of HPHT treatments and synthetic origins to safeguard asset value

Future Trends and Potential Applications

• Integration of machine learning for automated spectral interpretation and anomaly detection
• Development of portable FT-IR devices for in-field gem analysis
• Extension of the workflow to other gemstones and complementary spectroscopic methods
• Enhanced automation via robotic sample handling and advanced screening architectures

Conclusion

Bruker’s FT-IR based solutions deliver a robust, versatile platform for comprehensive diamond analysis. Their modular design and automated evaluation streamline routine workflows, offering precise type determination, treatment detection and imitation screening across a wide range of sample formats and throughput requirements.

Reference

• Bruker Optics (2021). FT-IR Diamond Analysis: Reliable identification and type determination by FT-IR spectroscopy. BOPT-01.
• Patents: DE102004025448; DE19940981.