Lab-grown diamonds (LGDs) are chemically and physically identical to natural diamonds, created in a controlled laboratory environment. A common question is whether these modern gems react to light like mined diamonds. Yes, lab-grown diamonds frequently exhibit a distinct glow when exposed to ultraviolet (UV) light. This phenomenon results from fluorescence and phosphorescence, triggered by trace elements captured during the diamond’s creation.
The Science Behind Diamond Glow
The visible glow results from UV light interacting with the diamond’s internal crystal structure. UV light is high-energy radiation that excites electrons within the diamond lattice, particularly those associated with defects or impurities. This energy causes electrons to temporarily jump to an unstable, higher energy state.
The electron immediately falls back to its stable state, releasing the absorbed energy as a photon of visible light. This process, known as fluorescence, only occurs while the diamond is exposed to the UV light source. The glow stops the instant the UV lamp is turned off.
Phosphorescence is a key characteristic in many lab-grown diamonds. Excited electrons become trapped in an intermediate energy state before returning to their ground state. They release energy more slowly, causing the diamond to continue glowing after the UV light source is removed. This lingering afterglow can last from a few seconds to several minutes, distinguishing it from instantaneous fluorescence.
Specific Fluorescence in HPHT and CVD Diamonds
Trace elements and structural defects introduced during manufacturing determine the color and intensity of the glow. Lab-grown diamonds are produced using two primary methods: High-Pressure/High-Temperature (HPHT) and Chemical Vapor Deposition (CVD). Each method leaves a distinct chemical signature that affects the diamond’s luminescent properties.
HPHT diamonds are often grown in the presence of boron, incorporated into the crystal structure. This inclusion typically results in a strong blue fluorescence when exposed to UV light. HPHT-grown diamonds also have a high propensity for phosphorescence, which can sometimes appear as orange, red, or greenish color after the UV light is turned off.
CVD diamonds, in contrast, frequently contain nitrogen-vacancy (NV) defects due to the growth process. These NV centers often cause the diamond to exhibit fluorescence in colors like orange, red, or greenish-yellow. Many CVD-grown diamonds also display a strong, sometimes prolonged, phosphorescence readily apparent under shortwave UV light. The color and duration of the afterglow are tied to the specific impurities and thermal treatments applied after growth.
Using UV Light to Identify Lab-Grown Diamonds
The unique luminescent properties of lab-grown diamonds provide gemologists with a powerful diagnostic tool for identification. While natural diamonds also fluoresce, their reaction to different UV wavelengths differs significantly from LGDs. Natural diamonds, if fluorescent, usually glow more brightly under longwave UV (LWUV), while lab-grown diamonds often show a stronger reaction under shortwave UV (SWUV).
The presence of strong and sustained phosphorescence is often the most telling indicator of a lab-grown origin, particularly in HPHT diamonds. This noticeable afterglow, lasting for seconds or minutes, is rare in natural diamonds, making its detection a strong red flag for a synthetic stone. Gemological laboratories use specialized SWUV and LWUV lamps to observe these reactions.
Beyond the color and duration of the glow, the distribution of fluorescence across the diamond’s surface is also diagnostic. Natural diamonds typically show an even, uniform fluorescence, but lab-grown diamonds often exhibit distinct growth patterns. HPHT diamonds may display a cross-shaped pattern or color zoning, visible under UV light, reflecting the crystal’s growth sectors. CVD diamonds can sometimes show a striped or layered pattern of fluorescence, corresponding to the sequential growth of the diamond film. These specific, non-uniform patterns, combined with strong phosphorescence, allow experts to confidently distinguish a lab-grown diamond from a natural one.