Lab-grown diamonds (synthetic or man-made) possess the identical chemical, physical, and optical properties of their natural counterparts. They are pure carbon crystals created by replicating the Earth’s high-heat and high-pressure conditions or using controlled chemical reactions. Because they are chemically identical to mined diamonds, they share many of the same optical characteristics. This leads to the question of whether they can “glow in the dark,” and the answer is yes, they can exhibit a temporary glow.
Understanding Diamond Luminescence
The “glow” observed in some diamonds is a scientific property called luminescence, which is the emission of light that is not caused by heat. This occurs when the diamond absorbs high-energy radiation, such as ultraviolet (UV) light, and then re-emits that energy as visible light. Luminescence is broadly categorized into two types based on the duration of the light emission.
The most common form is fluorescence, where the diamond emits a visible glow only while the external UV light source is actively stimulating it. The glow ceases almost instantaneously the moment the light source is removed. This effect occurs when energy excites electrons within the diamond’s crystal structure, causing them to release energy as visible light.
The specific phenomenon associated with a diamond truly “glowing in the dark” is phosphorescence, often referred to as the afterglow. Phosphorescence occurs when the diamond continues to emit light for a period of time after the stimulating UV source has been switched off. This afterglow can last from a few seconds up to several minutes, gradually fading away. The effect is caused by absorbed energy being trapped in the crystal lattice and slowly released as visible light. The length and intensity depend on the concentration of specific internal defects, and the color commonly appears as blue, green, or orange hues.
The Internal Causes of Luminescence in Lab Diamonds
The specific type and color of luminescence in any diamond is determined by the presence of trace elements and lattice defects within the crystal structure. These impurities act as luminescence centers; for instance, nitrogen is a primary trace element associated with blue fluorescence under UV light.
In lab-grown diamonds, the manufacturing method heavily influences the presence of these elements. The High-Pressure/High-Temperature (HPHT) method frequently utilizes boron, which is strongly associated with a blue phosphorescence. This makes HPHT diamonds more likely to display the afterglow effect than natural diamonds.
The Chemical Vapor Deposition (CVD) method grows diamonds layer by layer and often produces very pure diamonds with minimal nitrogen or boron content. Even so, these diamonds can exhibit luminescence due to structural defects, sometimes showing a weak, short-lived greenish phosphorescence after exposure to shortwave UV light.
In a laboratory, the concentration of trace elements is precisely controlled to achieve a desired outcome. This allows for the consistent production of diamonds with specific, identifiable luminescence signatures that are often more predictable than in natural stones.
How the Glow Relates to Value and Identification
The specific luminescence characteristics of a lab diamond are highly significant for professional gemologists, serving as a powerful tool for identification. Gemological laboratories use specialized equipment to study the color, intensity, and duration of both fluorescence and phosphorescence. Unique signatures, such as strong blue phosphorescence in an HPHT diamond, help differentiate lab-grown stones from natural ones.
For the consumer, the presence of phosphorescence rarely impacts the diamond’s visual appearance under normal lighting conditions. The afterglow effect is only visible in a very dark environment immediately following exposure to a powerful UV source. Standard gemological reports do not typically grade or mention phosphorescence, focusing instead on fluorescence.
The retail value of a lab diamond is generally not affected by the presence of phosphorescence. It is not considered a quality factor unless the luminescence is so intense that it causes a rare, visible milky or hazy appearance. Therefore, a lab diamond that exhibits an afterglow is not considered lower in quality or value for use in jewelry.