Therefore, you have to take other factors into account to assess durability
of a simulant. While moissanite is the hardest of diamond simulants on the
mohs scale (averaging at 9.25), it is also quite susceptible to chipping as
many jewelers and owners have discovered. This is probably why chipping is
not covered in the Moissanite limited warranty.

CZ based simulants will vary both in their Mohs rating and toughness rating.
Asha� rates at 8.5+, as do many other formulations, while other CZ's will
rate at 8.0. Toughness is difficult to measure per se, but our scientist did
find that our Asha� version3 proved much more difficult to shatter via
hammer blows than any other Asha� versions or other CZ simulants they
had tested. As a result of the v3 toughness improvement, Asha� now
warrants against chipping and fracturing under normal daily wear.


Retention of optical properties

While CZ simulants are generally the closest optical clones of a diamond,
one thing that has made them the bane of most self-respecting jewelry
owners is their notorious habit of changing color over time. Thus, many
customers who thought they were getting a good deal buying a cheap CZ
soon found out six months later they just had a plastic looking blob in
their ring. 

Since cheap CZ is just that, cheap, most manufacturers/jewelers dealing
in CZ simply took the approach of "just keep replacing the cz every year",
or else only mount it in cheap, throw-away type of jewelry. This in part is
what greatly damaged the reputation of CZ in most consumers eyes.

Thus, there was not much financial interest for anyone associated with CZ
simulants to actually do any scientific research into trying to understand
what caused color changes or clouding in CZ. For Asha�, we took the
opposite tact, that of trying to understand why and have made a lot of
progress on understanding why CZ changes color, and currently have a
very good working theory as to the molecular changes that cause the color
to change. Since we funded this work on our own, it will not be published as
we originally intended, but is part of the reason we warrant Asha� for the
lifetime of the owner against color change. Of interest/humor was the
number of reasons that were 'told' to us by people in the jewelry industry
about why many/most cz's don't hold their color, which proved to be
completely groundless in scientific testing. 


"A CZ is just a CZ"...right?

Only if "cubic carbon is just cubic carbon", yet as you know 'cubic carbon'
is diamond, and diamonds can vary widely in appearance, desirability, and
cost.  CZ is a shortened form of the term 'cubic zirconia', and comes from
the fact that many diamond simulants place an oxide of the metallic element
zirconium into a forced but stabilized cubic structure. However, that's all the
term addresses. Beyond that, the term cubic zirconia simply defines a range
of crystal recipes that can distort and change the physical and optical
properties of the zirconia unit cell, altering both optical and physical
characteristics as well as electrical conductivity.

For example, beyond the fact that zirconium is now in a cubic structure, all
other bets are off. To keep the zirconium in its cubic state, you have to add
what is termed a dopant - this is an element that will fill the missing holes
within the cubic unit cell in order to ensure it stays cubic at room
temperature. Dopant materials can include yttrium (YO2), calcium (CaOx),
MnOx, TiO2, etc. and just like adding different ingredients to a recipe, you
can then produce a different end-result. 

Chocolate makes a good analogy - all chocolate has at its core cocoa. But
few people will refuse to make further distinctions based on additional
ingredients, purity of the ingredients, proportions of the ingredients, etc.
which is why it's surprising to often see such simplistic thinking applied to
CZ-based simulants.

Also of interest - most jewelers will tell you that cubic zirconia is a man-
made only gem.  This, in fact, is not correct (check with the GIA), and the
proper full name is legally "synthetic cubic zirconia". The synthetic indicates
that it is the man-made equivalent of a natural gem.  Natural cubic-zirconia
does exist, in extremely rare conditions in nature.  However, because of its
rarity, the synthetic adjective is usually dropped.  

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