Brilliant optical wonders – from color stabilization to fire bloom

Cubic zirconia, a leader in the field of synthetic gemstones, is known for its outstanding optical properties and its near-diamond-like appearance. One of the most striking of these properties is its dazzling “fire”, a phenomenon that occurs when light passes through the stone and disperses it, breaking up white light into a rainbow of colors.

So why does synthetic cubic zirconia, the perfect substitute for diamonds, look better than diamonds?

It is mainly due to the difference in their physical properties, especially the refractive index and dispersion index.

Refractive index

The index of refraction is the degree to which light changes direction as it passes from one medium into another. A higher refractive index means that light is bent more drastically as it enters the gemstone, making it appear to sparkle more. Cubic zirconia has a refractive index of about 2.15 to 2.18, while diamonds have a refractive index of 2.417 (at the D line). Although diamonds have a higher refractive index, the high refractive index of CZ is still enough to produce an intense glow.

The so-called fire color is caused by the refracted light that passes through the gemstone. If light incident on the interior of a gemstone is reflected all the way through the small facets of the pavilion of the gemstone and out of the crown, the gemstone appears brilliant. As we humans are sensitive to yellow, blue and orange colors, the general reaction of fire to our eyes is yellow, blue and orange light.

Chromatic Dispersion

Dispersion is the ability of a gemstone to break down white light into its component colors, which is where the fire color comes from. Dispersion refers to the phenomenon whereby when white compound light passes through a material with prismatic properties, the material breaks up the compound light to form a spectrum of different wavelengths.

The dispersion value is a physical reflection of the intensity of a material’s dispersion. Theoretically, it is expressed by the difference between the refractive index of the material relative to red light (B=686.7 nm) and the refractive index of violet light (G=430.8 nm), and the larger the difference, the larger the dispersion intensity. Synthetic cubic zirconia has a dispersion index of 0.060, while diamond has a dispersion index of 0.044. This means that CZ is able to produce a wider range of colors and a more pronounced separation of colors when it breaks down light, and as a result, CZ displays a more colorful fire effect than diamond when exposed to light.

Cutting Process

In addition to the physical properties of the material itself, CZ’s fire color is closely related to the way it is cut. In order to maximize the fire effect, CZs are often cut with carefully designed proportions and angles that optimize the reflection and refraction of light within the stone, thus enhancing its fire performance.

At the same time, even though the fire color of a pinto is superior to that of a diamond, it has its own disadvantage in the area of brightness.

Because the gemstone’s facets are specifically designed for the physical properties of diamonds, they are able to create total internal reflection, which means that light from all angles is able to be emitted from the crown after it is incident on the inside of the diamond, which makes it look like the diamond has a very good brightness.

This standard round diamond shape has 58 facets. Divided into two parts, the top 33 facets of the crown include an octagonal table and 8 surrounding triangular star facets, 8 quadrilateral facets, and 16 triangular upper loops, while the bottom 25 facets include a very small octagonal base and 8 surrounding quadrilateral pavilion facets, and 16 triangular lower loops. Some small drills with no bottom face have 57 faces. The standard round diamond shape is a round diamond-type cut with face angles and proportions of the parts calculated according to modern optics, with a view to obtaining the best results.

The shape was originally designed based on the physical properties of the diamond, with the goal of achieving “total internal reflection” (TIR).

The internal cleanliness of a diamond has a significant impact on its brilliance. Internal imperfections or inclusions can interfere with the path of light, reducing both reflection and transmission and thus reducing brilliance. While high quality synthetic cubic zirconia is usually very clean internally, even small imperfections can affect the transmission of light and therefore its brilliance.

The mystery of color fading

Cubic zirconia has become a popular choice for many consumers in the jewelry market due to its brilliant luster and relatively low price. However, there are often questions about the durability of this man-made gemstone, especially whether it will fade over time.

Synthetic cubic zirconia is a man-made gemstone with optical properties similar to diamonds, such as a high refractive index and strong dispersion. Its chemical stability and physical hardness make it an ideal material for jewelry. The color of synthetic cubic zirconia can be adjusted by adding different metal oxides to meet the diverse needs of the market.

Fading usually refers to the gradual fading or disappearance of color over time or due to environmental factors. In the case of synthetic cubic zirconia, the likelihood of fading depends on two main factors: the source of the color and the surface treatment.

Color Sources

Internal metal oxides: If the color of synthetic cubic zirconia is caused by internally added metal oxides, such as cerium, chromium, neodymium, erbium, and titanium, these colors are stable and do not fade easily.

Surface Coatings: If the color of synthetic cubic zirconia originates from a surface coating, such as by vacuum spraying metal oxides to create a halo, this color may fade over time with wear or chemical attack.

Surface Treatments

Diamond-Like Carbon (DLC) Coating: Some synthetic cubic zirconia surfaces are coated with a layer of diamond-like carbon to increase hardness and wear resistance.

hardness and wear resistance. This treatment does not involve a color coating and therefore will not fade with wear.

Plating: Plating that is thin or of low quality may fade over time or in certain environments.

The chemical stability of cubic zirconia allows it to retain its color and luster for many years with normal use and proper care. Like all gemstones, it can be affected by certain environmental factors and chemicals that can cause slight changes in color.

Proper care and maintenance is the key to extending the life of cubic zirconia. The risk of fading can be minimized by avoiding prolonged exposure to direct sunlight, using mild detergents, and having your stone professionally cleaned when necessary.

Fading of cubic zirconia is not an insurmountable obstacle, and proper care is the key to maintaining the beauty and value of your gemstone, no matter what you choose. By taking the proper steps, cubic zirconia can maintain its brilliant luster and become a shining star in your jewelry box. Enjoy the beauty and charm of cubic zirconia together, while cherishing and protecting each piece of jewelry we hold dear.