What is the easiest way to determine if a stone is a diamond?

a diamond/moissanite tester. there are quite a few ways but that is the easiest.

Depends on your level of expertise…easiest for the untutored would be a diamond tester. However, as in most gemology, magnification is your best friend. Diamonds almost always have a sugary, bruted girdle, possibly naturals on the girdle which are diagnostic, and particular internal flaws which imitations and synthetics do not have…internal fractures, carbon spots, etc. If you study some photos from a diamond grading manual, it is easy to become familiar with these. The various substitutes also have characteristic inclusions that are different from those in a diamond.

While differentiating diamonds from substitutes should be fairly easy, distinguishing treated from untreated diamonds requires more expertise and distinguishing the latest synthetic diamonds from natural is, according to GIA, sometimes only possible with sophisticated lab tests. You might start by reading here:

The upshot is that some synthetics will show characteristics that standard gemological tests will show, while others will not. So you can kick out some synthetics, but others may fool you and will need to be sent to GIA for advanced testing.

Diamonds almost always have a sugary, bruted girdle, possibly naturals on the girdle which are diagnostic

This is a really poor method of determining if a gem is a diamond. Most diamond have faceted girdles. Most jewelry stores have diamond testers.

Hi @Richard_Hart3,

It wasn’t my intention to suggest that merely the presence of a sugary girdle proved the stone was a diamond, but that if magnification showed several characteristics of diamond, then it is a diamond. For instance, I don’t know of other stones that have naturals. Feathers in diamonds (fractures) are characteristic of diamonds. A lack of scratches indicates hardness. Diamond’s dispersion is fairly high, but lower than that of CZ or of strontium titanate. Of course, one would need some experience looking at many diamonds before using this approach. If the stone is quite flawless, there might not be any clues and then another approach would be necessary.

Hi, People are always bringing me stuff they think might be a diamond. CZ’s always look a bit pink to me. My first test, if it looks too good it probably isn’t real. I look for carbon with magnification. If the stone is loose, put it face down on small print. A diamond will break up the image and you won’t see any distinguishable lines. Put a CZ face down on fine print. If the lines are pure, if there is any distinguishable straight lines, it isn’t a diamond, I was told. Don’t know what moisonite does. If it is important I take it to a gemologist. I am not a gemologist.
In review, face down on fine print. Hope that is a bit helpful.

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A diamond tester is a good place to start but I have seen them give false readings. Looking under magnification is the next step. Inclusions are a good clue to it being diamond but not all diamonds have inclusions. If it is an older cut melee it may have the bruted girdle that was mentioned earlier or if it is more modern and larger it will have a faceted girdle. Every CZ I have ever seen has a smooth polished girdle, no facets. Look at the facet junctures, diamonds have very sharp edges where the facets meet. Softer stones have a more rounded juncture. Now comes the risky advice that many may not agree with. But it is a very good final test. Put a carbide separating disk in your flex shaft and running it very slowly lightly touch it to the girdle of the stone in question. It will have zero effect on a diamond no matter how fast you run it or how hard you press. All other stones will be scratched and if you are careful it will be a tiny scratch on the edge of a stone that is hard to notice and on a nearly worthless stone anyway.

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Careful. Read through only works on round diamonds halfway decently cut. You can read through almost all emerald cuts and many marquises. Demonstration of diamonds RI.