We’ve seen this scene in many movies and TV shows: someone has a diamond, but needs to prove that it is real. So, to do so, they attempt to cut or scratch glass with the stone. “It works!” “Yay, it’s a diamond!”
…Not so fast, “person-with-a-newly-ruined-mirror.”
The truth is, yes, diamonds cut glass, but this ability is not as unique as you may think.
In the early 1800’s, German geologist Friedrich Mohs designed the “Mohs scale of Mineral Hardness.” This scale ranges from 1 (the weakest) to 10 (the strongest). The measurement doubles at each level, so a mineral that is an 8 is considered twice as hard as a mineral that is rated a 7. A mineral that is a 9 is twice as hard as an 8 and 4 times as hard as the 7 and so on.
On the Mohs scale, diamonds are a 10; glass ranges between 6 and 7. So yes, diamonds can indeed cut and scratch glass, but so can quartz, emerald, topaz and cubic zirconia, as does anything else rated 7 or above.
So while diamonds can cut glass, so can many other minerals; this method is not as ideal as one may think to determine the legitimacy of diamonds. As well, using this method could dull or scratch the facets of your diamond, decreasing the value of the stone.
The biggest reason not to do this test is that diamonds aren’t as unbreakable as you think. The most fragile part of the diamond is along the girdle; this is the “waistline,” or widest part separating the top (the crown) and the bottom (the pavilion). Any exertion against the thin edge of the girdle could cause the stone to chip or break.
If you research the topic, there are numerous dubious ways to check if a diamond is real including submerging in water, attempting to read a newspaper through it or breathing on it. However, we here at Ouroboro Diamonds suggest taking your diamond (colour or white) to a certified gemologist to verify whether it is a legitimate or not. All diamonds that we sell already have certification from an independent third party, so with that verification in place, your mirrors and windows can sleep soundly knowing they won’t be put to the test!