Editor’s Note
This article examines deceptive practices in the diamond industry, where lab-grown stones or simulants are sometimes misrepresented as natural diamonds. As consumer preferences evolve, transparency about a diamond’s origin remains crucial to prevent fraud.
In an era dominated by natural diamonds, lab-grown diamonds and diamond simulants are often used as low-cost alternatives or to directly deceive consumers. Today, with the production cost of lab-grown diamonds decreasing and public aversion to traditional diamond advertising growing, more people are accepting the purchase of lab-grown diamonds or their substitutes. However, it constitutes outright fraud when merchants sell them at natural diamond prices or even falsely claim they are natural diamonds. The case exposed by CCTV involves using synthetic cubic zirconia (a type of zircon simulant) to impersonate lab-grown diamonds, profiting massively at a cost of one ten-thousandth of the price.
Diamond simulants mainly include synthetic cubic zirconia and synthetic moissanite. They resemble diamonds in appearance but can be distinguished by the naked eye through simple tests without professional instruments. For synthetic cubic zirconia, there are four easy-to-perform methods:
1. **Line Test**: Place the loose stone table-down on paper with a drawn line. A diamond will appear as a solid black area due to internal reflection, while lines will be visible through synthetic cubic zirconia.
2. **Grease Pen Test**: Utilizing diamond’s oleophilic nature, a grease pen line will be continuous and clear on a diamond but broken and discontinuous on synthetic cubic zirconia.
3. **Breath Test**: After breathing on the stone, the fog on a diamond dissipates instantly, while it lingers longer on synthetic cubic zirconia.
4. **Magnification Observation**: Diamonds often contain natural mineral inclusions or feathers, and their girdles appear frosted. Synthetic cubic zirconia is internally clean, and its girdle may show parallel polishing lines.
Distinguishing synthetic moissanite is more straightforward. Diamonds are singly refractive gems with sharp, single facet edges. In contrast, synthetic moissanite is doubly refractive with a high birefringence of 0.043. When viewed through the table with a 10x loupe, its facet edges appear doubled.
Although lab-grown and natural diamonds look similar, their growth environments and methods differ, requiring more in-depth techniques for visual distinction. Natural diamonds formed over a billion years ago under high temperature and pressure deep within the Earth, with crystals taking an octahedral shape. Lab-grown diamonds are rapidly synthesized in laboratories via two primary methods: HPHT and CVD.
HPHT (High-Pressure High-Temperature) synthetic diamonds mimic the natural process, using metal solvents like iron, nickel, or cobalt to crystallize carbon in a synthesis chamber over days or weeks. These diamonds often contain metallic inclusions that appear black and opaque in transmitted light and metallic in reflected light. They can even be attracted by a magnet due to the presence of nickel-iron flux.
CVD (Chemical Vapor Deposition) synthetic diamonds grow in a vacuum chamber using hydrocarbon gases, resulting in tabular crystals that require heat treatment to remove a brownish color.
For visual identification:
– HPHT diamonds, after cutting, may show a cross-shaped fluorescence pattern in the crown or pavilion.
– CVD diamonds may exhibit a striated pattern on the pavilion facets, with fluorescence colors including green, yellow-green, yellow, orange, and red.
While visual methods are effective, fraudulent practices have driven advancements in detection technology. The Natural Diamond Council launched the Natural Diamond Verification initiative in 2019, providing reliable, independent third-party verification. Diamond detection instruments (e.g., natural diamond screening devices) can accurately identify natural diamonds or distinguish synthetic ones, applicable to loose stones or set jewelry of various sizes. These instruments analyze growth patterns: natural diamonds exhibit a concentric growth pattern, HPHT synthetics show a cross-shaped pattern, and CVD synthetics display a striated pattern. Gemological experts utilize these tools to ensure market credibility and support consumer decision-making.
The fraud case exposed by CCTV reminds us that while distinguishing zircon impersonating lab-grown diamonds by the naked eye is possible, it requires knowledge of simple testing methods. When purchasing, consumers should prioritize reputable merchants and utilize professional testing to avoid losses. As detection technology becomes more widespread, market integrity will improve, allowing diamond consumption to reflect true value.