Sterling Silver Cubic Zirconia Jewelry

jayroweeson — Mon, 10 Nov 2008 09:57:36 +0100

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).

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 1976. Its main competition as
a synthetic gemstone is the more recently cultivated material,
synthetic moissanite.

As its name would imply, cubic zirconia
is crystallographically isometric, and as diamond is also isometric,
this is an important attribute of a would-be diamond simulant.
Synthesized material contains a certain mole percentage (7-20%) of
metal oxide stabilizer.[citation needed] During synthesis zirconium
oxide would otherwise form monoclinic crystals, its stable form under
normal atmospheric conditions. The stabilizer is required for cubic
crystal formation; for example CZ
rings and cubic
zirconia earrings it may be typically either yttrium or calcium
oxide, the amount and 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 5.6–6.0. Cubic zirconia is relatively
hard, at about 8.5 on the Mohs scale— much harder than most natural
gems. Its refractive index is high at 2.15–2.18 (B-G interval) and
its luster is subadamantine. Its dispersion is very high at
0.058–0.066, exceeding that of diamond (0.044). Cubic
zirconia bracelets and CZ
pendants has no cleavage and exhibits a conchoidal fracture. It
is considered brittle. It is considered brittle because although it
has a hardness of 8.5 it can still easily be fractured because the
hardness of a mineral refers to its tendency of being scratched.

Under shortwave UV cubic
zirconia necklaces and dog
tags typically luminesces 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 recent years manufacturers have
sought ways of distinguishing their product by supposedly "improving"
cubic
zirconia anklets. Coating finished CZs in a film of diamond-like
carbon (DLC) or Amorphous Diamond is one such innovation, a process
using chemical vapor deposition. The resulting material is
purportedly harder, more lustrous and more like diamond overall: The
coating is thought to quench the excess fire of CZ, while improving
its refractive index, thus bringing it more in line with diamond.
Additionally, because of the high percentage of diamond bonds in the
amorphous diamond coating, the finished simulant will show a positive
diamond signature under Raman spectroscopy.

Another technique first applied to
quartz and topaz has also been adapted to bangles
/ cuffs : Vacuum-sputtering an extremely thin layer of metal oxide
(typically gold) onto the finished stones creates an iridescent
effect. This material is marketed as "mystic" by many
dealers. Unlike DLC, the surreal effect is not permanent, as abrasion
easily removes the oxide layer.

There are a few key features of cubic
zirconia silver sets which distinguish it from diamond, some
observable only under the microscope or loupe, for example:[citation
needed]

* Dispersion: With a dispersive
power greater than diamond (0.060 vs. 0.044) the more prismatic fire
of cubic
zirconia charms can be seen by even an untrained eye.

* Hardness: Cubic zirconia has an
8.5 to <9.0 on the Mohs hardness scale vs. a rating of 10 for
diamonds.

* Specific gravity: Cubic zirconia
crystals are heavyweights in comparison to diamonds; a cubic zirconia
will weigh about 1.7 times more than a diamond of equivalent size.

* Flaws: Contemporary production of
cubic zirconia is virtually flawless,[citation needed] whereas most
diamonds have some sort of defect, be it a feather, included crystal,
or perhaps a remnant of an original crystal face (e.g. trigons).

* Refractive index: CZ
cufflinks has a refractive index of 2.176, compared to a
diamond's 2.417.

* Cut: Under close inspection with
a loupe, the facet shapes of some cubic zirconias appear different
from diamonds.

* Color (or more precisely, the
lack thereof): Only the rarest of diamonds are truly colorless, most
having a tinge of yellow or brown to some extent. By comparison,
cubic zirconia can be made in most cases entirely colorless:
equivalent to a perfect "D" on diamond's color grading
scale.

* Thermal conductivity: Cubic
zirconias are thermal insulators while diamonds are among the most
efficient thermal conductors, exceeding copper. This makes telling
the difference between diamond and cubic zirconia quite easy for
those with the right instruments.

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Sterling Silver Cubic Zirconia Jewelry