A Diamond That Breaks the Rules: The Mystery of Red Fluorescence in a Natural Diamond 

For centuries, diamonds have mesmerized the world with their brilliance, beauty, and rarity. Yet, beyond their stunning appearance, diamonds hold secrets that advanced laboratories, like GSI,  work tirelessly to uncover. 

As the production of laboratory-grown diamonds (LGDs) becomes increasingly sophisticated, so  does the challenge of distinguishing them from natural diamonds. While LGDs share many optical and physical properties with their natural counterparts, cutting-edge gemological laboratories utilize state-of-the-art screening instruments to accurately differentiate between them. 

A key factor in this identification process is fluorescence, a characteristic that offers valuable insight into a diamond’s growth history. Fluorescence has long served as an essential tool for distinguishing between natural and lab-grown diamonds. However, what happens when a diamond challenges conventional wisdom? 

Fluorescence as a Diagnostic Tool 

Diamonds react to UV light in varying ways based on their atomic structure and trace elements. When exposed to ultraviolet (UV) light, natural diamonds generally exhibit a blue fluorescence due to nitrogen-related defects. In contrast, laboratory-grown diamonds display a broader range of fluorescence hues. CVD diamonds often fluoresce in shades of red, orange, pink, purple, or yellow, while HPHT diamonds typically emit a turquoise-blue fluorescence. This difference has made fluorescence a reliable preliminary screening method worldwide. However, as with all rules, exceptions exist. 

A recent study conducted by GSI led to a remarkable discovery; a natural diamond, part of a bracelet, displayed red fluorescence, a trait almost exclusively associated with CVD lab-grown diamonds. Such occurrences are extremely rare and open intriguing discussions in diamond characterization. 
Fluorescence in natural diamonds is influenced by their trace-element composition and structural defects. In rare cases, fancy-colored diamonds, such as the famous Hope Diamond, exhibit red fluorescence due to specific boron-related defects. However, finding a colorless or near-colorless natural diamond with red fluorescence is very uncommon. Also, it is a challenge for the trade who would clearly conclude this particular diamond in natural diamond jewelry as a lab-grown diamond. This unexpected phenomenon underscores the need for advanced testing beyond traditional fluorescence screening. 

Beyond Fluorescence: The Science Behind Advanced Testing 

To ensure precise identification, GSI utilizes advanced screening instruments that utilize photoluminescence spectroscopy. These instruments analyze both fluorescence (which fades quickly after UV exposure) and phosphorescence (a lingering glow). When fluorescence raises suspicion, advanced techniques like infrared and Raman spectroscopy are used to examine a diamond’s growth structure, strain patterns, and trace-element composition. 

For diamonds flagged for further testing, such as this rare red-fluorescing natural diamond, additional analysis helps confirm its authenticity. Spectroscopic studies can reveal whether the fluorescence results from unusual nitrogen-vacancy centers, structural distortions, or other atomic-scale anomalies, thus deepening our understanding of diamond formation. 

Why This Matters for Retailers and trade 

For jewelry retailers and trade, this discovery highlights the importance of advanced testing and expert verification. Relying solely on fluorescence for diamond identification can sometimes lead to misinterpretations. A natural diamond with red fluorescence could be mistaken for a lab-grown diamond, potentially affecting its valuation and the trust of consumers. 

The diamond industry is evolving, and as lab-grown diamonds grow more sophisticated, ensuring authenticity requires more than traditional tests. As LGDs continue to improve in quality and complexity, the jewelry industry must remain vigilant. The discovery of a naturally occurring red-fluorescing diamond emphasizes the need for continuous innovation in detection technology. Advanced gemological expertise and next-generation analytical instruments will play a crucial role in preserving the integrity of the gem & jewelry trade. 

At GSI, rigorous continuous scientific research, cutting-edge technology, and global collaboration ensure that even the most elusive anomalies are detected with precision and shared with the industry. As the industry evolves, laboratories must not only keep up but set new standards for excellence in diamond authentication.

By Ramit Kapur, MD, Gemological Science International (GSI)