Rendering Salt & Pepper Diamonds


I use Rhino and have managed to render most colour stones effortlessly, however I find Salt and Pepper Diamonds to be tricky.

I am wondering if someone has figured out a way to render realistic salt and pepper diamonds. I have seen most people render a ‘grey’ diamond, but is there a way to get the lovely inclusions to be more prominent? If anyone has figured out a trick or two I would greatly appreciate any advice.

Warm Regards,

what is that? i had to google it since i never heard of it and i am still not entirely sure how that should look like.

if you have a reference please include it

shows diamonds with impurities in it.

You can probably do this by adding the tiniest objects inside your gem object and giving them useful materials.

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Hi Encephalon,
Reference image:

thanks nathan, now i understand. so these are natural inclusions of carbon and whatever is left over sometimes even smaller diamonds. i am not a jewellery guy, but these look more appealing than the clear and stupidly expensive pendent.

i would offset some of the facets as surfaces and put a transparent png with some grey carbonish texture on and render the rest as a slightly smokey diamond.

the problem is that i noticed recently trying that transparent png do not render in cylces. i think i forgot to make a bug report, can you confirm that?

Hi Nathan,

My thoughts exactly. Its a bit of a round a bout way. I suppose no one has really tried it and mostly render a grey stone to get a similar effect, but its not quite the same.


I have the past week done several tests with transparent PNGs, they all worked fine. I used

orange_thingy_with_alpha, which I (not so skillfully) handcrafted myself!


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i am rubbing my eyes,… it seems to work now :man_shrugging: did you change something recently?

@Luché_Oberholzer i had a quick go using the idea i described above,

i think that could work as a starting point.

I haven’t changed shader code in a looooong time.

ok… i keep rubbing my eyes then.

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Amazing! Thank you. Definitely a starting point!

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here a version with some refraction, still scratching my head how to emulate caustics though.