All About Gem Cuts, Part 2!
In this blog I’m going to delve deeper into what gem cutting all about and I will discuss three components that are additional to what I wrote about in part one. If you haven't read part one, you can check it out here.
A variety of gem cuts (image accessed via New World Gem)
The gem cutter has to consider, among many things, the gems Refractive Index. The higher this number the shallower and steeper the pavilion (bottom part of the gem) can be. The lower the refractive index (RI) then the deeper the pavilion should be. RI refers to the gems ability to bend and slow light...the more it does this the easier it is to cut the gem to give it a sparkle.
In the case of lower RI stones, like quartz, we have to develop a deeper pavilion with more facets in order to prevent light from leaking out the bottom and redirecting it back to your eye....without this, the gem looks dead. So why aren’t all proportions done perfectly? We are limited by the initial size of the rough we have to work with so perfect proportions aren’t always possible. If we cut too much of the gem material away then the cost increases possibly to the point where the customer will not pay for this level of perfection. It’s a balancing act between brilliance versus value. Striking that balance gives you a good looking gem but one that you can actually afford to own.
Raw Quartz (via New Moon Beginnings) Cut Quartz in Gems en Vogue Honker
The natural size of the rough will always dictate how well a stone is proportioned and in some species, thinner stones are normal and cannot be avoided. Ruby is a classic example. Most ruby rough is flat and thin so obtaining a deep stone is often impossible, especially in smaller sizes. Luckily this gem has a higher RI value and a deeper color which in unison compensate for this so the wearer, they do not see a difference.
Rough Ruby (via Gem Society) Various Cuts of Ruby (via GIA)
A third important component of cutting is the final polish. When a gem is finally faceted the facets are a bit rough and hazy and need to be polished. The quality and polishing material used can either make or break the visual appeal of the stone. A good polish leaves no surface lines and a smooth, mirror-like finish. Of course, this costs more but in the end is critical.
In conclusion, the overall goal is to render an affordable gem that is cut well but at the same time is obtainable and affordable for everyone.