Just FYI to those for whom accuracy (either to diamond, or to the film prop) factors heavily into their choice of material:
I looked up out of curiosity the weight of cubic zirconia relative to diamond, crystal glass, and quartz (
I assume most likely the "rock crystal" of the original prop, though anyone by all means correct me), and I was surprised to discover that my gut sense of gem density seems to have been rather poorly-calibrated. Not meaning to add complication, but I figure others similarly may find the following surprising, and possibly helpful:
*** Cubic zirconia is
far denser than diamond, and in fact on the far upper end of density for gems as a whole.
Probably most of us have handled a piece of hematite; it's heavier than that!
*** Crystal glass, meanwhile, is generally less dense than diamond, but
not as far off as one might expect, and
denser than quartz.
Here's a comparison of
specific gravities (weight ratio to water, or grams per cubic cm) for commonly-recognizable gems:
5.5-6.0 ...
cubic zirconia (CZ)
5.1-5.3 ... hematite
4.0-4.1 ... ruby
3.9-4.0 ... sapphire
3.9-4.3 ... garnet (most common form)
3.5-3.6 ... topaz
3.5 ...........
diamond
3.1-3.2 ... moissanite (closest diamond substitute - far pricier than CZ)
~3.0 ........
glass, "crystal" (either lead, or newer lead-free barium/zinc additive)
2.8-3.1 ... tourmaline (most common form)
2.7-2.8 ... emerald
2.7 ...........
quartz ("rock crystal")
2.6 ........... agate
~2.5 ........ glass, regular
Of course, hardness is also a factor. Here's approximately how the same list gets
re-ordered by the Mohs hardness scale:
10 .......
diamond
9.5 ...... moissanite (closest diamond substitute)
9.0 ...... ruby
9.0 ...... sapphire
8.5 ......
cubic zirconia (CZ)
8.0 ...... topaz
7.5 ...... emerald
7.5 ...... garnet
7.5 ...... tourmaline
7.0 ......
quartz ("rock crystal")
7.0 ...... agate
6.0 ...... hematite
~6.0 ...
glass ("crystal" & regular
)
And we can't forget shimmer. Here's the same list
re-ordered by refractive index (ratio of speed of light in air vs. in medium):
2.9-3.2 ... hematite
2.6-2.7 ... moissanite (closest diamond sustitute)
2.4 ...........
diamond
2.1-2.2 ...
cubic zirconia (CZ)
1.7-1.8 ... garnet
1.7-1.8 ... ruby
1.7-1.8 ... sapphire
~1.7 ........
glass, "crystal"
1.6-1.7 ... tourmaline
1.6-1.7 ... topaz
1.5-1.6 ... emerald
1.5-1.6 ...
quartz ("rock crystal")
1.5-1.6 ... agate
~1.5 ........ glass, regular
So for folks desiring accuracy, this raises a little bit of a conundrum.
CZ remains by far the more accurate to diamond in hardness and shimmer; more similarly scratch-resistent, and more convincing visually.
If you happen to above-all value accuracy in weight, though (either to diamond
OR the film prop), then you might prefer crystal glass.
By the same token, noting where quartz falls on the refractive index, you might also prefer crystal glass if you value above-all accuracy in shimmer to the film prop (keeping in mind that a film set is often extremely brightly lit).
Personally, I'm sticking with CZ regardless; the idea of a diamond having substantial heft just feels more intuitive – perhaps due to the natural association with weighty precious metals. Plus, I doubt I'll ever have the opportunity to handle a diamond anywhere approaching the Pink Panther's size, so it's not like my sense of verisimilitude is in danger of being contradicted by tangible experience. But I could picture this making a difference to some, so I thought it was worth clarifying.
[Any mineralogists out there, let me know if you spot an error.]
