Scientific and factual, but biased towards our Asha�
version3 cz-based
simulant.
Notes: this article is a work in progress, and as such may
at times be in need
of correction, modification or clarification.
If you have additional commentary or corrections, please
email us!
[this article may not be reprinted, and is copyright
BetterThanDiamond.com,
2001]
Achieving the diamond-look via
man-made gems
If you want to look like a diamond,
then your crystal has to handle light in
approximately the same way that diamond does.
Diamond's crystal structure is cubic, specifically
"face-centered-cubic".
Common logic would indicate
that if you want your crystal to replicate the
optics of a cubic crystal, your crystal should be
cubic as well. CZ-based
simulants such as Asha� are
thus cubic, specifically "face-centered cubic"
as
well. Moissanite, in contrast, has a hexagonal
crystal structure.
The signature optical characteristic of a cubic
crystal is that the velocity of
light is constant as
it passes through the gem regardless of which way
the
light enters. Gems that handle light in such a
democratic fashion are termed
"singly refractive",
meaning they let light through at a constant speed.
Other
crystal structures will let light pass through
at one speed if they enter from
certain directions,
and slow it down more if it enters from other
directions.
This is termed "doubly-refractive", or
two different light velocities.
An analogy may help you remember it better: imagine
a crystal structure as
a town. If the town sets it
so that the speed limit for all roads in the town
is
55mph, then regardless of which road you entered the
town on, you could
pass through the town the entire
way at 55mph. This would be a single-
speed limit
town, or a singly refractive gem.
Now take another town - this town sets the speed
limit at 55mph for certain
roads, but other roads it
forces you to only travel at 25mph. Thus,
depending
on which exit you took to enter into the town, you
might be
traveling through the town at 25mph or
55mph. This would be analogous to a
"doubly-refractive" gem. The net result of such a
system would be that some
light would pass through
quickly at 55mph, and other light would only pass
through at 25mph. Scientist measure the difference
using "birefringence" or
the difference in speed
between the highest speed limit and lowest speed
limit in the town.
Because light cannot pass through a
'doubly-refractive' gem at the same
speed, it tends
to give it a "fuzzy" or "blurry" appearance to the
eye.
Moissanite of course is doubly-refractive, and
it is one optical characteristic
that makes its
appearance different than diamond.
Hardness + Toughness = How long your gem will
last, or durability.
While many people often look to the Mohs hardness
scale in an effort to
make a rough estimation of how
long a diamond simulant will last, this is
actually
only part of the picture. The Mohs scale is a scale
of relative
resistance to scratching, with the
emphasis on relative. Diamond is the top
pillar on
the Mohs scale, set at 10. Talc is at the bottom,
set at 1.
Depending on who can scratch who, other
gemstones take their relative
order in this system.
(note: The Mohs hardness scale is very imprecise and
in some ways misleading, and usally results in
approximations rather than
specific measurements -
however, it is the best known scale to the
average
person).
However, while diamond is virtually impervious to
scratching, it can be
broken with a hard blow (as
many diamond owners have discovered upon
finding
chips on the girdle of their gem). On the flip side,
Jade can be
easily scratched, yet is one of the
toughest materials known. The difference
is Jade
has an interlocking crystal network. Thus, hardness
can also result
in brittleness, just as softness can
also enhance resistance to breakage/
fracturing.
