Hello everyone! I’m new here, and I’m an amateur… I’ve been selling antique costume jewelry for over a decade but looking to learn gemstones more now. This is probably an easy and dumb question for any gemologist, but I would love a little help and clarity.
I have this ring which I originally thought may be a diamond, but now I believe it is a moissanite, although I’m not certain. I have been trying to compare the ring to a known diamond earring under a microscope (certainly not the best microscope as I’m just starting out), and I’m trying to see the differences. I was having trouble seeing and identifying double refraction with a loupe, probably just because I haven’t really seen it before, but is that what I am seeing under the microscope in the pictures? Sometimes I felt like if I turn it the right way I would see the facets more clearly, and other times I guess it looks doubled.
My second question is this; do diamonds give off any rainbow coloring at all? I know that moissanites do, and I can certainly see it more so with the naked eye, but I just want to make sure diamonds do not as well. Just wondering for future purchases, if I see any pronounced rainbow coloring, I can assume it is likely not a natural diamond?
The ring’s stone has a pretty big chip as well, so I’m hoping that wasn’t affecting the way the facets looked.
Thank you all for any help and clarification!
-Eric
diamond is on the right
The edge is chipped as seen above
The next two pictures are of the stone in question in the ring below
The next two pictures are of the diamond earring below
Greetings Eric! Welcome to the forum!
Both Moissanite and Diamond display good dispersion (rainbow effect) and Moissanite can be higher.
Yes, Moissanite is doubly refractive. The image under the microscope does seem to show that. The chip on the stone could effect the observation of this depending on the light path and viewing angle.
Here is a good comparison on their respective properties.
Cheers!
Thanks so much for the help Troy! Much appreciated for lending a hand to the beginner. That link you provided was helpful, and when I did the UV test before it was a bit yellow in color so that makes sense. I’ll work on doing a RI test just for future comparisons and practice. Thanks!
You are most welcome!
An RI test for Diamonds and Moissanite is not easily achieved. The standard refractometer stops at 1.81.
One test that can help distinguish the two is a specific gravity test. Diamond has a typical SG of 3.51 - 3.53 and Moissanite has a max of 3.22. This test does require the stone to be removed from the setting. A scale with a resolution down to 0.01ct /0.002 grams or better, can be used for most stones. The smaller the stone, the more precision the scale needs to have.
Here is a good reference for tests that may or may not help with Identifying Moissanite
Cheers!
Fantastic, I thought I heard that the RI wasn’t a great test for moissanite before, so that makes sense. I’ll have to get some SG equipment soon. Great reference chart, thanks so much!
The polariscope will show whether the stone is diamond or moissanite because if you rotate the stone between crossed polars there will be no great change in transmitted light with diamond which belongs to the cubic crystal system unlike moissanite. This may be difficult to see if the stones are mounted in jewellery and if the facets confuse the light transmission.
Good information. I was curious if a polariscope could be used here but hesitated to suggest.
Thanks!
Thank you guys very much for all the help. I’m excited to get a polariscope and play around with it 
