Buzz
A rough diamond is an uncut diamond. To determine whether the stone in your hand is a diamond, you can quickly assess it visually to eliminate other gemstones. Afterward, you can perform more precise tests using corundum or an electronic diamond tester. You can also conduct a gravity test to determine the stone's density and confirm whether it’s a diamond or not.
Steps
Perform simple at-home tests
Look at the stone from above and count the edges. Diamonds have a cubic crystal structure, while stones like quartz have a hexagonal shape. Look at the top of the stone and count the edges. If you count 4 edges, the stone is likely a diamond. If there are 6 edges, it could be quartz.
- Visual inspection is a quick way to rule out other gemstones, but it’s not a definitive test.
- If you see 4 edges, use additional methods to confirm it is a diamond.
Diamonds can have various shapes, but the most common is a 12-faceted pyramid-like structure with stacked layers.
Kennon Young
Gemstone Expert
Gemstone Expert
Rub the stone against a piece of corundum. Corundum is another mineral that is slightly softer than diamond. You can purchase a small piece of corundum cheaply or buy a mineral testing kit that includes corundum. Hold the piece of corundum firmly on a table and rub the suspected diamond against it. If scratches appear on the corundum, the stone you’re testing is a diamond. If no marks appear, the stone is likely another mineral.
- The Mohs scale of hardness ranks minerals based on their hardness. Diamonds are ranked 10 on the scale, while corundum is ranked 9. This explains why corundum gets scratched when rubbed against a diamond.
Use a diamond tester pen instead of scratch tests. You can purchase a diamond tester pen online. Check the green light to ensure the device is fully charged. Press the tip of the tester pen onto the stone you suspect is a diamond. If the pen beeps and the light illuminates, the stone is a diamond. If not, it might be another gemstone.
- Diamond testers use electrical conductivity and thermal conductivity to determine whether a gemstone is a diamond.
- Cheaper diamond testers might not be as accurate as more expensive models.
- Be sure to read customer reviews before purchasing a diamond tester.
Perform a density test
Weigh the stone using an electronic scale and record its weight. You can purchase an electronic scale online. Place the stone on the scale and note down the recorded weight on a piece of paper.
- Some electronic scales are more accurate than others. Look for one with at least 2-3 decimal places after the integer.
Fill a cup with water and set the scale to zero. Pour enough water into a paper or plastic cup to fully submerge the stone. Place the cup of water on the scale and press the “tare” button to reset the display to zero.
- Resetting the scale to zero helps determine the density of the diamond without factoring in the weight of the cup or water.
- If you don't have a plastic cup, you can also use a lightweight Tupperware container or a plastic bowl.
- Ensure that the container does not extend beyond the edge of the scale.
Wrap a paperclip around the stone so you can suspend it in the water. To determine the stone’s density, you need to suspend it in the water without it touching the bottom or sides of the cup. Straighten a paperclip and wrap one end around the widest part of the stone securely. Hold the other end to lift the stone and keep it suspended in the water.
Submerge the stone completely in the water and record its weight. Use the other end of the paperclip to lower the stone into the water, making sure it doesn't touch the sides or bottom of the cup. Record the weight measurement on the same piece of paper where you noted the stone's original weight.
- If the stone touches the sides or bottom of the cup, the scale will give an inaccurate reading.
- The weight of the paperclip is negligible.
Divide the stone's weight by its weight in water. By dividing the stone's weight by its suspended weight in water, you will get its density. Diamonds have a density of – 3 g/cm3. If your calculation result is lower than this, the stone is likely another gemstone. If the result is close to this number, it’s very likely your stone is a diamond.
- For example, if the stone weighs 12.6 g and its weight in water is 4.8 g, the result of the calculation will be 2.625, which is close to the density of quartz, not diamond.
Check if the density of the stone falls within the range of – 3 g/cm3. You may have a diamond in your possession if your calculation falls within the range of – 3 g/cm3. For example, if your stone weighs 16.84 g and its weight in water is 4.8 g, you would calculate 16.84 g / 4.8 g = 1 g/cm3. This result shows that the stone's density matches that of a diamond.
- If you determine that you truly have a diamond, it is recommended to have it evaluated by a professional gemologist.
Perform additional verification methods
Determine if the diamond originated near kimberlite pipes. Kimberlite pipes are volcanic rock formations that arise from molten magma and are found beneath the earth's surface. Natural diamonds are primarily discovered in kimberlite pipes. If your diamond comes from a kimberlite pipe, it is highly likely to be a diamond and not another type of stone.
Kennon Young
Gemstone Expert
Gemstone Expert
Diamonds can also be found in water. Diamonds are discovered within cratons, the oldest and most stable part of the Earth's crust. Diamonds can also be carried away from cratons and flow with water currents, which is why they can also be found in streams or even oceans at the end of water flows.
Use a magnifying glass or a 10x loupe to closely inspect the stone. A loupe is a special magnifying tool used by jewelers. Place the diamond under the loupe or microscope to look for rounded edges with tiny, concave triangular marks. On the other hand, cubic diamonds tend to have parallelogram or rotated square shapes. Genuine diamonds appear to have a thin layer of vaseline coating them.
- A cut diamond will have sharp, defined edges.
Take the diamond to an expert for evaluation if you're still unsure. If you've conducted various tests and believe the stone in your hand is a diamond, take it to a professional for confirmation. In the United States, you can also receive a certificate of authenticity along with a report number from GIA (Gemological Institute of America) or another recognized diamond grading organization.
- Having the diamond professionally appraised is the most reliable way to determine whether the stone is a diamond.
What You Will Need
Identifying Rough Diamonds
- Corundum
- Diamond Tester
Perform the Gravity Test
- Digital Scale
- Cup
- Water
- Paper
- Pencil
- Calculator
Try Other Testing Methods
- Microscope or Magnifying Glass
