Moissanite, a popular diamond alternative, is a gemstone known for its remarkable brilliance and durability. Chemically, it is silicon carbide (SiC), a compound of silicon and carbon. It offers a comparable look to diamond at a different price point. The story of moissanite’s origin is unique, beginning not in an earth mine but in an extraterrestrial crater. The vast majority of moissanite available today is created in a laboratory.
The Cosmic Origin and Discovery
The original natural material is extraterrestrial in origin. In 1893, French chemist Henri Moissan discovered minute quantities of the mineral while examining rock samples from the Canyon Diablo meteorite crater in Arizona. He initially mistook the shimmering crystals for diamonds. Further analysis revealed the material was silicon carbide, a compound previously unknown in nature.
The mineral was later named moissanite in his honor. Natural moissanite is exceedingly rare on Earth, confined to tiny crystals found in meteorites and deep-earth rock formations, such as kimberlite pipes. The small size and scarcity of these natural crystals mean they are not viable for commercial jewelry production. For decades, moissanite remained a scientific curiosity until synthetic processes were developed.
Chemical Structure and Unique Properties
Moissanite’s characteristics stem from its composition as silicon carbide (SiC). This compound features a crystal lattice structure held together by strong covalent bonds between silicon and carbon atoms. The strength of these bonds results in impressive physical properties.
The material registers approximately 9.25 on the Mohs scale of hardness, ranking it second only to diamond. This high hardness makes moissanite extremely resistant to scratching and abrasion, ensuring its suitability for daily wear jewelry.
Beyond its durability, moissanite is prized for its exceptional optical performance. It possesses a high refractive index, ranging from 2.65 to 2.69, which is higher than that of a diamond. This allows the gemstone to slow down and bend light more effectively, resulting in superior brilliance.
The gem exhibits a high dispersion rate, measured at 0.104, which is more than twice the dispersion of a diamond. Dispersion is the ability of a gemstone to separate white light into its component spectral colors, often called “fire.” This high dispersion is responsible for the intense, rainbow-like flashes of color that moissanite is known for.
Synthetic Production for Commercial Use
Nearly all moissanite used in commercial jewelry today is grown in a laboratory. This synthetic material is chemically identical to the natural version, but its creation is controlled and reproducible. Growing gem-quality silicon carbide crystals is complex, requiring a high-temperature, controlled environment.
The most common technique for producing moissanite is the seeded sublimation process, a modification of the original Lely method. This process involves heating silicon carbide powder to extremely high temperatures, often exceeding 2,500 degrees Celsius, inside a specialized graphite crucible.
The silicon carbide powder sublimates, turning directly into a gas without passing through a liquid phase. This gas then recrystallizes onto a small, pre-existing moissanite seed crystal in a cooler section of the crucible. The controlled environment allows the crystal to grow slowly over two to three months, producing large, high-purity single crystals suitable for cutting.
This synthetic process overcomes the scarcity of natural moissanite, making the durable gemstone widely available for jewelry and high-tech applications, such as electronics and abrasives.