If you have a good diamond simulant, then you really need to take it to a trained jeweler in order to distinguish between it and a real diamond. There is a myth out there that you can tell the difference between a simulant and a real diamond by attempting to scratch glass with the stone. Don't even think of trying this test if you value your stone. There are two reasons why this is a bad test.
First of all, glass has a hardness on Mohs scale of only 5.5 (http://www.bbc.co.uk/dna/h2g2/A2982576). As you can see from the table given at the following link (http://en.wikipedia.org/wiki/Diamond_simulants#Summary_table), most of the good simulants have hardnesses that are higher than this. This means that most simulants will scratch glass. There are only two diamond simulants that are not harder than glass is, rhinestone and Strontium titanate. Rhinestone is not harder than glass because it is glass. Additionally, it is easy to distinguish from diamond because the back side (pavilion) has to be mirrored in order to give it the same sparkle as diamond. Strontium titanate is really not used much anymore because there are better simulants now.
The second reason why this is a bad test is because diamonds have cleavage. Cleavage consists of one or more planes of weakness (cleavage planes) within the structure of a mineral. When a mineral with cleavage is placed under stress, then it will tend to break along these cleavage planes. Diamond has four planes of perfect cleavage. So, when you use a diamond to scratch a pane of glass, the stress that you place on the stone could cause the stone to chip or (more rarely) crack. In either event, this would reduce the value of the stone. (This, by the way, is also why the test DownOnMyLuck suggested is not a good idea.)
So, trying to scratch glass with a gemstone to see if it is a diamond is a bad test because the ability to scratch glass is not unique to a diamond and, if it is real, you could damage your stone in the process of testing it. So, if you have doubts about the authenticity of a stone that someone claims is a diamond, then you should take it to a reputable jeweler and have him look at it.
I also have one last piece of advice for you ladies. If you have reason to believe that the "diamond" that your man has given you is not real, then I would suggest that your relationship has more problems than a fake diamond. If you don't trust your man, then maybe you should reevaluate your relationship.
Comments
I will just comment on the first test listed here. That one will depend on the cut of the stone and the quality. If the stone is not a well cut round brilliant, then it may give a false negative as to whether it is a diamond. Also, if it is a well cut round brilliant, then this test will not separate good simulants from the real thing. It would only help you distinguish glass and quarts from the better stones.
by Glenn Blaylock on October 2nd, 2007
mmm...okay. Thanks for the clarification Glenn!
by GiraffeyedDonor-ish on October 2nd, 2007
I found another site that tells "how to test a diamond".
You can find additional information at www.starstruckllc.com/diamonds-real-or-fake.html
It saw very informative.
by Anonymous on January 19th, 2009