Jewelry, Gems, & Minerals/rough diamonds


I was given rough gems from a relative back in the 70's.  My husband thought they may be uncut diamonds in various colors by scratching a glass window to check them.  Our window is streaked with scratch lines.
Are you knowledgeable in determining if these rough stones (non-polished) could be diamonds?
I haven't attached a picture because I believe there is a physical test that is required-if so, where is the best place to take them and what would be the cost?

Actually there is a very simple test that is indicative for a possible diamond. Diamonds are very hydrophobic, which means that they repel water. The majority of other gems and semi precious stones are not. Let me explain.

When you put water in a glass and watch the edges where the water touches the glass you will notice that the water "curls" up on the side of the glass. It appears a little higher. This is true for materials that attract water, like other rocks, minerals and gems. But NOT for diamonds, because they will always repel water.

Here is a simple but very revealing test.

Take a different gem first, like a quartz or even a glass marble and clean thoroughly with soap and water first, then rinse very, very well. Without touching, handling the object with tweezers let the non-diamond dry thoroughly and then submerse in rubbing alcohol, swirling it around for a few minutes. Again, handle only with tweezers, remove the stone from the alcohol bath and let it dry thoroughly. It is important NOT to contaminate the objects with any skin oils. Now use the tweezers and place the non-diamond in the middle of a dish. Carefully add water to the side of the dish until the stone in the middle is 1/3 submersed. Now watch the edges of the water against the non-diamond. It will curl up clinging to the stone. Keep the dish and the stone as a reference as you prepare your suspected diamonds in the same way , testing them in a second dish as follows.

Clean your suspected diamonds in the same way and and do not handle them except with tweezers. Again, you don't want body oils even in minute quantities clinging to the sample. Now place the thoroughly dried suspected diamonds on the second plate and add water as with the other stones. If your suspected diamonds are true diamonds, the water WILL CURL DOWNWARD. Compare this to the other non-diamonds in the first dish and if your suspected diamonds are indeed diamonds you will really be able to see the difference. Diamonds are about the only gem that will do that without fail, every time because they repel water.

If the water curls up as well on your suspected diamonds then these are NOT diamonds.

This is a simple, but very effective and revealing test. Just make sure that no oils cling to the diamond since this may falsify the results. Hence the intricate cleaning procedures beforehand.  

Jewelry, Gems, & Minerals

All Answers

Answers by Expert:

Ask Experts


Uwe Richard Kackstaetter, Ph.D. (Dr.K)


I can answer questions concerning minerals, mineralogy, gems, metals, and anything that has to do with geology. However, I am NOT a jeweler. Questions about values, settings, gem stone cuts and appraisals are best directed to other experts on this site. I can however aide in the identification of unknown mineral materials. As a public service and part as training for new geoscientists, our university department provides FREE mineral identification for individuals. Please contact me for details or go to for details..


I am a professor of applied geology and mineralogy with many hours of field experience. Furthermore, I enjoy recreational gold prospecting and mineral collecting. As a professor I am engaged in research concerning minerals and their occurrence.

Member of the GPAA (Gold Prospectors Association of America) as well as the Association of Environmental Geochemists. Member of the GSA (Geologic Society of America) Member of the AIPG (American Institute of Professional Geologists)

Here is a small sampling: Mineral-rock handbook: Rapid-easy mineral-rock determination : written for anyone interested in minerals and rocks - Proctor, Peterson, and Kackstaetter;Macmillan Pub. Co. (New York and Toronto and New York) Physical Geology Laboratory e-Manual [CD-ROM], Kackstaetter, Earth Science Education LLC Colorado Front Range Self-guided Geology Field Trips, Kackstaetter,

Ph.D. in Applied Geology and Mineralogy. I am actively teaching courses in mineralogy and a variety of field courses with mineral collecting opportunities. Background in precious metal exploration.

Past/Present Clients

©2016 All rights reserved.