Lab-grown diamonds (LGDs) are synthetically grown carbon structures that are chemically, physically, and optically identical to their earth-mined counterparts. Despite being created in highly controlled laboratory environments, these gems are not perfectly flawless. Like natural diamonds, LGDs contain internal imperfections, known as inclusions, and surface irregularities, called blemishes, which form during crystallization. LGDs possess structural imperfections and are graded for clarity just like any mined diamond.
The Origin of Imperfections
The two primary methods used to grow diamonds in a lab, High-Pressure/High-Temperature (HPHT) and Chemical Vapor Deposition (CVD), both involve conditions that inevitably introduce structural irregularities. The controlled environment attempts to mimic the diamond formation process deep within the Earth, but it does so at an accelerated pace. This rapid, non-equilibrium growth is the fundamental reason why inclusions and internal strain patterns develop within the crystal lattice.
The HPHT method uses a metal solvent-catalyst, often containing iron, nickel, or cobalt, to dissolve the carbon source material. When the diamond crystallizes from this molten flux, microscopic droplets of the metal mixture can become physically trapped within the growing diamond structure. These residual materials become the characteristic metallic inclusions seen in HPHT stones.
The CVD process, in contrast, involves breaking down carbon-rich gases in a vacuum chamber, allowing carbon atoms to precipitate onto a diamond seed layer by layer. CVD diamonds are prone to imperfections such as non-diamond carbon, or graphite, resulting from incomplete or inconsistent carbon deposition. Fluctuating temperature and pressure conditions during growth can also induce internal strain, creating unique stress patterns within the finished crystal.
Distinct Types of Inclusions in Lab Diamonds
The specific nature of a lab-grown diamond’s imperfection often serves as a fingerprint of its creation method. HPHT diamonds are identified by the presence of metallic inclusions, which appear as small, opaque, or reflective dark spots when viewed under magnification. Because the metal flux is electrically conductive, these inclusions can sometimes be detected by specialized equipment.
CVD diamonds are characterized by dark graphite or non-diamond carbon inclusions that look like tiny black pinpoints or clouds within the crystal. Another key feature in CVD stones is the presence of parallel, linear growth striations, which are faint growth lines visible under high magnification. These striations are a direct result of the layer-by-layer growth process.
Unique internal growth patterns also manifest as distinctive strain patterns. HPHT diamonds exhibit cuboctahedral growth, while CVD diamonds show columnar growth. These growth sectors, visible only with advanced gemological tools, are internal structural flaws. Their presence is what prevents an LGD from achieving a Flawless clarity grade.
Clarity Grading and the Consumer
The presence and nature of these imperfections directly impact the diamond’s official clarity grade, one of the “Four Cs” used to evaluate diamond quality. Gemological laboratories use the same clarity scale for lab-grown diamonds as they do for natural diamonds, ranging from Flawless (FL) to Included (I). This scale dictates the stone’s grade based on the size, number, location, relief, and nature of the inclusions when viewed under 10x magnification.
Most lab-grown diamonds fall into the Very Slightly Included (VS) and Slightly Included (SI) ranges. This is often due to the controlled production environment yielding a cleaner result than the unpredictable geological process. A VS grade indicates minor inclusions that are difficult to see under 10x magnification, while SI indicates noticeable inclusions. For the average consumer, the vast majority of lab-grown diamonds are “eye-clean,” meaning the imperfections are not visible without a jeweler’s loupe. The size and placement of an inclusion are the primary factors determining the final price and visual appearance.
Differentiation from Natural Diamond Flaws
Both lab-grown and natural diamonds are crystallized carbon with flaws, but the composition and morphology of those flaws are the primary diagnostic tools for gemologists. Natural diamonds typically contain mineral inclusions, such as olivine, garnet, or small diamond crystals. They also frequently exhibit features like feathers (tiny internal fractures) and twinning wisps, which reflect billions of years of intense and chaotic geological formation.
Lab-grown diamonds display flaws characteristic of their rapid, synthesized growth. The metallic inclusions found in HPHT stones are never present in natural diamonds and will attract a strong magnet, which is a clear identifier of a lab origin. The specific geometric or linear growth patterns seen in LGDs are also distinctly different from the irregular, organic growth structures of mined diamonds. The type of flaw acts as a unique chemical and structural signature, allowing experts to definitively determine the stone’s origin.