Since lab-grown diamonds are chemically, physically, and optically identical to mined diamonds, it is impossible to distinguish between them with the naked eye or even with basic jeweler’s tools like a standard diamond tester (which only checks for thermal conductivity).
However, trained gemologists and specialized laboratory equipment can definitively determine a diamond’s origin by looking for subtle differences in its formation.
Here are the most reliable methods used to tell if a diamond is lab-grown:
1. Check the Grading Report (The Easiest Way)
The most straightforward and reliable way to know the origin of a diamond is to look at its independent grading report (certificate) from a reputable gemological lab like GIA, IGI, or GCAL.
- Lab-Grown Diamonds will be clearly labeled with a designation such as “LAB GROWN,” “LABORATORY-CREATED,” or “CVD/HPHT” (referring to the creation method).
- Mined (Natural) Diamonds will be labeled as “NATURAL.”
2. Look for the Laser Inscription
Most certified lab-grown diamonds have a microscopic laser inscription on the girdle (the diamond’s widest edge) that identifies its origin.
- This inscription is usually a report number and a phrase like “LAB GROWN” or “LG”.
- It requires a jeweler’s loupe (usually 10x magnification or more) or a microscope to read.
3. Specialized Gemological Testing (For Experts)
When the certificate or inscription is unavailable, experts use advanced scientific tools to find markers related to the diamond’s growth process:
- Growth Patterns: Natural diamonds form in an octahedral (eight-sided) shape, creating specific internal growth structures. Lab-grown diamonds (especially CVD) can exhibit more uniform, sometimes layered, or metallic inclusions due to their rapid, controlled growth. These subtle differences are visible only under high-magnification and specialized lighting.
- Fluorescence and Phosphorescence: When exposed to short-wave ultraviolet (UV) light, lab-grown diamonds often exhibit a distinctive fluorescence or, more commonly, phosphorescence (a glow that continues briefly after the UV source is removed) that differs from natural diamonds. For example, some CVD diamonds can show an orange or reddish glow.
- Spectroscopy: Advanced equipment uses light (like Infrared or Raman spectroscopy) to analyze the diamond’s atomic structure and identify trace elements. Natural diamonds usually contain trace amounts of nitrogen, while many lab-grown diamonds (especially CVD) are Type IIa, meaning they are exceptionally pure with no detectable nitrogen. This “too pure” composition is a strong indicator of a lab origin.
