The rising interest in diamonds has led to curiosity about alternatives, particularly those referred to as “fake diamonds.” This term encompasses a range of materials with distinct compositions and origins. Understanding these differences and how they are created in laboratories provides clarity regarding their properties and value.
Defining “Fake” Diamonds
The term “fake diamond” can be misleading, as it refers to two categories: diamond simulants and lab-grown diamonds. Diamond simulants are materials that visually resemble natural diamonds but possess different chemical and physical properties. They are not carbon-based and merely imitate a diamond’s appearance. Examples include Cubic Zirconia and Moissanite.
In contrast, lab-grown diamonds, also known as synthetic or laboratory-created diamonds, are genuine diamonds. They share the exact same chemical, physical, and optical properties as natural diamonds formed geologically within the Earth. The primary distinction lies in their origin: one is mined from the Earth, while the other is created in a controlled laboratory environment. The Federal Trade Commission (FTC) has recognized lab-grown diamonds as real diamonds.
Manufacturing Diamond Simulants
Diamond simulants are engineered to mimic the visual appeal of natural diamonds. Cubic Zirconia (CZ) is a widely recognized simulant, produced from zirconium dioxide (ZrO2). Its manufacturing often involves a process called skull melting, where zirconium oxide powder, mixed with a stabilizer like yttrium oxide, is heated to over 3,000°C in a water-cooled copper crucible. This method allows the material to melt from the inside out, forming cubic crystals as it cools. CZ is known for its brilliance and dispersion, often exhibiting more rainbow flashes than a diamond.
Moissanite, another popular simulant, is composed of silicon carbide (SiC). While naturally rare, the moissanite used in jewelry is almost exclusively lab-grown. The manufacturing process for moissanite involves combining silicon and carbon under high-temperature and high-pressure conditions, often through methods like the Lely process or Physical Vapor Transport (PVT). Moissanite has a higher refractive index and typically displays more “fire,” or rainbow flashes, than a diamond. Other less common simulants include Strontium Titanate and Yttrium Aluminum Garnet (YAG).
Producing Lab-Grown Diamonds
Lab-grown diamonds are synthesized using technologies that replicate the extreme conditions under which natural diamonds form. The two primary methods are High-Pressure/High-Temperature (HPHT) and Chemical Vapor Deposition (CVD). Both processes begin with a small diamond seed crystal.
The HPHT method mimics natural diamond formation deep within the Earth’s mantle. A diamond seed is placed in a growth chamber with a carbon source, such as graphite, and a metal catalyst (like iron, nickel, or cobalt). This assembly is subjected to immense pressures, typically around 5-6 GPa, and high temperatures, ranging from 1,300°C to 1,600°C. The molten metal dissolves the carbon, which then precipitates and crystallizes onto the diamond seed. This process can take several days to weeks.
The CVD method involves growing diamonds from a carbon-rich gas mixture in a vacuum chamber. A diamond seed is placed inside the chamber, heated to temperatures between 700°C and 1,200°C. Carbon-containing gases, such as methane and hydrogen, are introduced. A microwave beam breaks down the gas molecules, creating a plasma cloud, and carbon atoms deposit onto the diamond seed. CVD growth typically occurs over several weeks.
Identifying Non-Natural Diamonds
Distinguishing between natural diamonds, lab-grown diamonds, and diamond simulants requires careful examination. Visual inspection can offer initial clues. Cubic Zirconia often exhibits excessive rainbow flashes and tends to be perfectly colorless and internally flawless, unlike most natural diamonds which typically have some inclusions. Moissanite also shows a higher “fire” or rainbow effect than diamonds and may have a noticeable doubling of facet junctions under magnification due to its double refraction.
Thermal conductivity is another key differentiator. Diamond testers measure how quickly heat passes through the stone; natural and lab-grown diamonds are excellent heat conductors, while simulants like CZ conduct heat differently. A simple “fog test” can also be indicative: breathing on a diamond will cause the fog to dissipate almost immediately due to its high thermal conductivity, whereas a CZ will remain foggy for several seconds. Differences in weight or specific gravity can also be observed; for instance, a CZ will weigh approximately 1.7 times more than a diamond of the same size. For definitive identification, especially between natural and lab-grown diamonds, specialized gemological equipment and professional testing are necessary. Lab-grown diamonds are often inscribed with a microscopic mark on their girdle indicating their origin, which can be seen under magnification.