The phrase “high carbon diamond” is not a formal scientific or gemological classification, but rather a commercial or colloquial term used in the jewelry market. This descriptor is employed to emphasize the purity of a stone’s composition. The term is sometimes used to market lab-grown diamonds, underscoring their chemical identity with natural stones. In other, less accurate contexts, the phrase can be misleadingly applied to certain diamond simulants.
The Fundamental Chemistry of All Diamonds
Every true diamond, regardless of its origin, is an allotrope of the element carbon, meaning its chemical formula is simply ‘C’. This structure involves carbon atoms bonded together in a rigid, three-dimensional lattice. Each carbon atom forms strong covalent bonds with four neighboring carbon atoms, creating a dense tetrahedral network. This specific atomic arrangement is responsible for the extreme hardness and durability that diamonds are known for, registering a 10 on the Mohs scale.
The immense strength of the carbon-carbon bonds gives the material its unique physical properties, including its exceptional thermal conductivity. Trace elements, such as nitrogen or boron, may be present in the structure, but they account for less than 0.05 percent of the stone’s total composition. Therefore, all diamonds are “high carbon” materials because they are composed almost entirely of pure, crystallized carbon.
Commercial Context: Why the Term “High Carbon” is Used
In the commercial jewelry industry, the phrase “high carbon diamond” is most often used to distinguish genuine lab-grown diamonds from non-carbon diamond alternatives. Lab-grown diamonds, created using methods like High-Pressure/High-Temperature (HPHT) or Chemical Vapor Deposition (CVD), are chemically and physically identical to their mined counterparts. Marketing them as “high carbon” serves to assure consumers they are purchasing a stone that is verifiably pure carbon.
The term also relates to the concept of diamond purity, which gemologists classify using diamond types. Diamonds are categorized by the type and amount of chemical impurities within their structure, usually nitrogen. The Type IIa diamond, which makes up less than 2% of all natural diamonds, is the purest form, containing virtually no measurable nitrogen or other trace elements. These Type IIa stones are effectively 99.95% or more carbon.
Some marketers use “high carbon” to reference this exceptional purity, implying the stone possesses the superior optical properties associated with Type IIa diamonds. Lab-grown diamonds are often created with extremely high purity, which allows them to achieve the colorless and highly transparent qualities of the Type IIa classification.
Distinguishing High Carbon Diamonds from Simulants
The application of the “high carbon” label can become confusing when it is incorrectly associated with diamond simulants. Simulants are materials that look like a diamond but do not share its chemical composition or crystal structure. The two most common simulants are Moissanite and Cubic Zirconia (CZ), and neither can accurately be called a “high carbon diamond.”
Moissanite is chemically known as silicon carbide, with a formula of SiC. While it contains carbon, the presence of silicon atoms means it is a compound, not pure carbon, and therefore its lattice structure is fundamentally different from a diamond’s. Cubic Zirconia is an entirely synthetic material composed of zirconium dioxide, or ZrO₂. This material contains no carbon at all, making its inaccurate use of the “high carbon” label particularly misleading.
Some manufacturers of simulants, especially Cubic Zirconia, may apply a carbon-based coating to enhance the material’s durability or brilliance. Even with this coating, the core of the stone remains zirconium dioxide, and it does not transform the material into a diamond.