What is a CZ?
What is a CZ or Cubic Zirconia? A Cubic Zirconia is different than a Cubic Zirconium, although the public uses the terms interchangeably.
Cubic zirconia (or CZ) is the cubic crystalline form of zirconium dioxide (ZrO2). The synthesized material is hard, optically flawless and usually colorless, but may be made in a variety of different colors. It should not be confused with zircon, which is a zirconium silicate (ZrSiO4). It is sometimes erroneously called “cubic zirconium”. The flawlessness of the CZ is why you can get a more perfect sparkle than a diamond.
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Because of its low cost, durability, and close visual likeness to diamond, synthetic cubic zirconia has remained the most gemologically and economically important competitor for diamonds since commercial production began in 1976. Its main competitor as a synthetic gemstone is the more recently cultivated material, synthetic moissanite. Moissanite tends to have a darker color than the Cubic Zirconia.
Some Scientific Facts about the CZ
For those of you who want to dig further about your new CZ and it’s properties, read on.
Cubic zirconia is crystallographically isometric, an important attribute of a would-be diamond simulant. During synthesis zirconium oxide would naturally form monoclinic crystals, its stable form under normal atmospheric conditions. A stabilizer is required for cubic crystals to form, and remain stable at ordinary temperatures; this may be typically either yttrium or calcium oxide, the amount of stabilizer used depending on the many recipes of individual manufacturers. Therefore the physical and optical properties of synthesized CZ vary, all values being ranges.
It is a dense substance, with a specific gravity between 5.6 and 6.0 — at least 1.6 times that of diamond. Cubic zirconia is relatively hard, at about 8 on the Mohs scale— slightly harder than most semi-precious natural gems.[ Its refractive index is high at 2.15–2.18 (compared to 2.42 for diamonds) and its luster is adamantine. Its dispersion is very high at 0.058–0.066, exceeding that of diamond (0.044). Cubic zirconia has no cleavage and exhibits a conchoidal fracture. Because of its high hardness, it is generally considered brittle.
Under shortwave UV cubic zirconia typically fluoresces a yellow, greenish yellow or “beige”. Under longwave UV the effect is greatly diminished, with a whitish glow sometimes being seen. Colored stones may show a strong, complex rare earth absorption spectrum. In white light or sunlight, the color of the stone reflects it’s natural color – which is the color your purchased it. The new CZ’s do not degrade, discolor or deviate from the stone in which you purchased. Just like with diamonds, you get what you pay for.
2 Comments
February 11th, 2012 at 11:22 pm
CZs were originally developed by the Russians, for their space program. They were developed as an alternative to diamonds that were used in the optics of their lasers. CZs have a refractive index, dispersion and hardness so close to a diamond it’s uncanny.
So what are some key features that can guide you in telling the difference between diamond and CZ? Do keep in mind, though, in order to accurately distinguish the two gems, gemological equipment such as microscope, or loupe, must be used for testing and verification.
To start, let’s take a look at the hardness factor: Did you know CZ ranges between 8.5 to 9.0 on the Mohs’ hardness scale, whereas diamond, one of the hardest materials known to man, is rated 10, lying at the top of the hardness scale?
Furthermore, glass (or sand) is rated approximately 5 to 6 on the hardness scale, therefore, dust and dirt will not scratch CZ. Indeed, CZ can scratch glass just like regular diamonds, making it more resistant to chipping.
One great difference between diamond and CZ is weight. CZs are heavyweights in comparison to diamonds; a CZ will weigh approximately 1.75 times more than a diamond of equivalent size. So basically, a piece of CZ the same size as a one-carat diamond weighs about 1.75 carats. Well…isn’t that interesting?
Contemporary production of CZ is virtually flawless, whereas diamond usually contains impurities and inclusions, or have some sort of defect, be it a feather, included crystal, or perhaps a remnant of an original crystal face (e.g. trigons).
In regards to color-more precisely, the lack of color-only the rarest of diamonds are truly colorless, as most have a tinge of yellow or brown to some extent. By comparison, CZ in most cases can be made entirely colorless, equivalent to a perfect “D” on diamond’s color grading scale.
Also, under close inspection with a loupe, the facet shapes of some CZs appear different from diamonds. Both gems disperse light a little differently. Dispersion is just a scientific term for the breaking up of light into its spectral colors. With a dispersive power greater than diamond (0.060 vs. 0.044), the more prismatic fire of CZ can be seen by even an untrained eye.
March 19th, 2012 at 12:24 am
These are more sparkly than diamonds. Unbelievable.