DiamondAvenue.com - Facts About Diamond Simulants
Diamond Simulants
A diamond simulant is a material that resembles a diamond in appearance but has a different chemical composition, crystal structure and physical or optical properties.
Two of the best-known modern diamond simulants are cubic zirconia (CZ) and synthetic moissanite. Both can provide considerable brilliance and sparkle, but neither is actually diamond.
What Is a Diamond Simulant?
Diamond simulants are gemstones or manufactured materials chosen because they can imitate some of diamond's visual qualities.
A simulant may be natural or laboratory-made, but its chemical composition and crystal structure are fundamentally different from those of diamond.
Examples of materials that have been used as diamond simulants include cubic zirconia, synthetic moissanite, colorless sapphire, zircon, quartz, glass and several other transparent materials.
Simulants Are Not Lab-Grown Diamonds
A laboratory-grown diamond should not be confused with a diamond simulant.
Laboratory-grown diamonds have essentially the same carbon crystal structure and many of the same chemical, physical and optical properties as natural diamonds.
Cubic zirconia and synthetic moissanite merely imitate certain aspects of a diamond's appearance. They are different materials and can be distinguished through appropriate gemological testing.
Cubic Zirconia
Cubic zirconia, commonly abbreviated CZ, is one of the most familiar diamond simulants. It is a synthetic crystalline form of zirconium oxide and became widely available for jewelry during the late 1970s.
CZ can be manufactured as a colorless material or in many colors. When well cut and polished, colorless CZ can closely resemble diamond to the unaided eye, but its gemological properties differ substantially.
Hardness
Diamond has a hardness of 10 on the Mohs scale and is the hardest naturally occurring mineral.
Cubic zirconia generally measures approximately 8 to 8.5 on the Mohs scale.
CZ is therefore durable enough for many jewelry applications, but it can scratch and abrade more readily than diamond.
Density
Cubic zirconia is substantially denser than diamond.
Diamond has a specific gravity of approximately 3.52, while cubic zirconia is commonly around 5.6 to 6.0.
As a result, a CZ and a diamond of approximately the same physical dimensions will not weigh the same. The cubic zirconia will generally be considerably heavier.
Refractive Index
Refractive index describes how strongly a gemstone bends light passing through it.
Diamond has a refractive index of approximately 2.42, while cubic zirconia is approximately 2.15 to 2.18.
This difference contributes to the distinctive optical appearance of each material.
Color
Cubic zirconia can be manufactured in a highly colorless form and can also be produced in many attractive colors.
Depending upon the manufacturing process and added elements, CZ may be produced in shades including yellow, pink, purple, green, blue and other colors.
Natural diamonds also occur in many colors, but their color is the result of natural structural features, trace elements or other processes within the diamond.
Facets & Appearance
The quality of cutting and polishing affects the appearance of any transparent gemstone.
Under magnification, CZ may sometimes show facet edges and surface features that differ from those ordinarily expected on a well-cut diamond.
Visual appearance alone, however, should not be relied upon for a conclusive identification. Gemological testing provides a more dependable determination.
Why Cubic Zirconia Became Popular
Cubic zirconia became one of the world's best-known diamond simulants because it can be manufactured in large quantities, cut into many shapes and sizes, and produced with excellent transparency and a bright, diamond-like appearance.
It offers the visual effect of a colorless gemstone at a substantially different price point from natural diamond, although its durability, density and optical properties are distinctly different.
Synthetic Moissanite
Moissanite is silicon carbide. Natural moissanite is extremely rare, while the moissanite commonly used in jewelry is produced synthetically.
The mineral is named for French scientist Henri Moissan, who identified natural silicon carbide in material associated with the Canyon Diablo meteorite in Arizona.
Near-colorless synthetic moissanite became an important diamond simulant for jewelry during the late 1990s. It is known for its high hardness, brilliance and especially strong dispersion or "fire."
Hardness
Synthetic moissanite has a Mohs hardness of about 9.25.
That makes it harder than most gemstones and suitable for jewelry exposed to regular wear, although diamond remains harder at Mohs 10.
Double Refraction
Unlike diamond, synthetic moissanite is doubly refractive.
When examined from certain directions under magnification, some facet junctions may appear doubled. This can help a trained gemologist distinguish moissanite from diamond.
Fire & Dispersion
Moissanite has significantly stronger dispersion than diamond. Dispersion is the splitting of white light into spectral colors commonly called fire.
This means moissanite can display pronounced flashes of rainbow color, particularly in larger stones and under certain lighting conditions.
Refractive Index
Synthetic moissanite has refractive indices of approximately 2.65 and 2.69, compared with approximately 2.42 for diamond.
Combined with its strong dispersion, this gives moissanite considerable brilliance and colorful flashes of fire.
Density
Synthetic moissanite has a specific gravity of about 3.22, compared with approximately 3.52 for diamond.
A moissanite therefore weighs somewhat less than a diamond of comparable physical dimensions.
Diamond vs. Cubic Zirconia vs. Moissanite
Although the three materials can appear similar at first glance, their physical and optical properties provide reliable ways to distinguish them.
Diamond
Composition:
Carbon
Mohs Hardness:
10
Refractive Index:
Approximately 2.42
Specific Gravity:
Approximately 3.52
Optical Character:
Singly refractive
Cubic Zirconia
Composition:
Zirconium oxide
Mohs Hardness:
Approximately 8 to 8.5
Refractive Index:
Approximately 2.15 to 2.18
Specific Gravity:
Approximately 5.6 to 6.0
Optical Character:
Singly refractive
Synthetic Moissanite
Composition:
Silicon carbide
Mohs Hardness:
Approximately 9.25
Refractive Index:
Approximately 2.65 to 2.69
Specific Gravity:
Approximately 3.22
Optical Character:
Doubly refractive
Identifying a Diamond Simulant
Experienced gemologists can distinguish diamonds from simulants using combinations of optical observations and gemological testing.
Characteristics that may be evaluated include refractive behavior, density, dispersion, electrical or thermal response, microscopic features and spectroscopy.
No single visual characteristic should be considered conclusive for every stone.
A Note About Diamond Testers
Some traditional thermal diamond testers can readily distinguish cubic zirconia from diamond.
Moissanite presents a greater challenge because its thermal properties can resemble those of diamond closely enough that some thermal probes may identify moissanite as diamond.
Modern screening instruments and additional gemological tests can distinguish natural diamonds, laboratory-grown diamonds and common simulants more reliably.
Similar Appearance, Different Gemstones
Cubic zirconia and synthetic moissanite can both provide attractive diamond-like appearances, but they are fundamentally different materials from diamond.
Understanding hardness, density, refractive properties, dispersion and composition makes it easier to understand why these materials look similar while behaving differently.
Most importantly, consumers should know whether the gemstone they are purchasing is a natural diamond, laboratory-grown diamond or diamond simulant.