May I add something here, and I’m no rendering experts, but a long time handmade goldsmith + stone setter [in a none commercial way].
One problem I ofter see in jewellery renderings is that the gemstones mostly looks synthetic or treated, and rarely feels natural. and as far as I understand this, a way to deal with that will be to include physical [or material based or both] inclusion, + some shade variation for gems like Rubies.
So the render does need to have the ability to capture intersecting objects inside transparent gemstones.
An option to ignore is certainly an important feature. saving the need to [in some cases] of having to make one version of the model for printing and another one for rendering.
*another jewellery rendering challenge would be to find a way to render the inner light phenomena [can’t remember the correct English term] in gemstones like high-end star sapphire where the star is generated by microscopic rutile crystals arranged in hexagonal structure inside the translucent gemstone.
The only way I know now, of how to render such stone is to apply an image to the surface. but that looks fake.
thanks a lot