Is it possible for a real diamond to scratch glass? The answer is yes—a diamond can scratch all types of glass. Diamonds are so hard that they can even scratch other diamonds. But what other gemstones can scratch glass? And is scratching glass a reliable way to tell if a diamond is real or fake?
A real diamond can scratch glass, as can other gemstones harder than glass, including cubic zirconia and moissanite. Test a stone by looking for inclusions under a microscope. You can also put the gem over a newspaper. If you can read the print through the stone, it’s probably not a diamond.
Let’s look at how a real diamond can scratch glass and whether fake diamonds can do the same. You’ll also learn other ways to tell if a diamond is real.
Can a Real Diamond Scratch Glass?
Genuine diamonds are the hardest natural material on Earth, made up of closely packed carbon atoms arranged in a diamond cubic crystal structure. This arrangement makes diamonds extremely strong.
The Mohs scale is a way of measuring the hardness of materials. It rates them from 1 (softest) to 10 (hardest). Diamonds are ranked 10 on the Mohs scale, meaning they’re harder than any other natural material. Diamonds are so hard that they can even scratch other diamonds.
Glass is rated 6-7 on the Mohs scale. So, diamonds can also scratch all types of glass, including window glass, drinking glasses, and eyeglasses.
The hardness of diamonds also makes them useful in industrial applications like cutting and drilling. For example, diamond-tipped saws and drill bits can cut through almost any material, including stone, metal, and concrete.
So, if you’ve ever wondered whether a diamond can scratch glass, the answer is yes. But what about fake diamonds? Can they scratch glass, too?
Can Fake Diamonds Scratch Glass?
Most fake diamonds are cubic zirconia (CZ) or moissanite. Cubic zirconia is a manufactured material harder than glass but softer than diamonds. Moissanite is a natural silicon carbide crystal that’s also harder than glass but softer than diamonds.
Cubic zirconia and moissanite are rated 8.5-9.5 on the Mohs scale. So, these fake diamonds are also harder than glass and can scratch it.
Because both cubic zirconia and moissanite are harder than glass, scratching glass is not a reliable way to tell if a diamond is real. However, there are other ways to differentiate between a genuine diamond and a fake one.
What Other Ways Can You Tell if Diamond is Real?
To determine whether a diamond is real, you can do other tests to check its properties. Each test has advantages and disadvantages, so it’s best to do more than one.
Cup the stone in your hand and breathe on it as if you were fogging a mirror.
Because diamonds are good at conducting heat, the fog from your breath should quickly disperse if it’s a real diamond. However, if the fog lingers, it’s probably a fake diamond since cubic zirconia and moissanite will retain the heat from your breath longer.
The breath test is not foolproof, however. For example, if the stone is very small or set in a piece of jewelry, the heat from your hand might disperse the fog rapidly.
If you don’t have a loupe, you can use a magnifying glass with at least 10x magnification.
Look at the diamond closely and check for inclusions—internal imperfections of tiny minerals or fractures that occur when the diamond forms. Inclusions may appear as dark spots, clouds, or microcrystals.
Genuine diamonds usually have inclusions, but they shouldn’t be visible to the naked eye. Fake diamonds will often appear flawless under a magnifying glass. However, some real diamonds appear flawless. So, this test isn’t reliable by itself.
Place the diamond on a newspaper. If you can read the print through the stone, it’s probably not a real diamond. Diamonds bend light differently than other materials, so you shouldn’t be able to read the newspaper through it.
Cubic zirconia, moissanite, and other fake diamonds will often allow you to read the print on a newspaper. However, some diamonds with few facets will also allow you to read the print. So, this test isn’t foolproof either.
The best way to tell if a diamond is real is to take it to a qualified jeweler and have it professionally tested. A professional can use specialized equipment to determine whether a stone is a diamond or a fake.