Important notes on diamond and moissanite testing

This article is a sub-article of the larger one we have made on the differences between various stones. In that article, we went in-depth with the testing of stones set in jewelry. However, this article will cover a few notes and details regarding the testing of stones and what to be aware of and look out for in general, no matter where the jewelry is from or what stones are mounted in it.

To quickly recap, there are two main types of testers for natural diamonds, lab diamonds, and moissanite. There are pen testers and box testers. For more specific information, please read through our other article on the different stones here: Article Link (Click Here), which explains the different testers.

One of the first important notes regarding testers is that there are good and bad testers. This is especially true for pen testers. If you have someone test anything with a tester like the one shown below:

You should be very careful with believing whatever result comes from it. They are cheap $10 - $20 testers, which are known for being inaccurate and producing a high number of false positive results. 95% of the time, if you test the new types of moissanite on one of those machines, it will show up as a diamond. The thing is, they just don't compare to the components of counterparts that cost hundreds of dollars.

Although it can ensure you aren’t dealing with CZ stones while thinking it is a diamond or moissanite, it will most definitely be able to show moissanite as a diamond. Especially with the development of moissanite factories trying to make the diamond simulant as much like a diamond by even adding diamond powder on the stones, making it even trickier to detect if it is real or not.

To clarify, of course, the tester obviously isn’t specifically made to check for moissanite vs. diamond parameters. However, it is made to test the thermal conductivity of the stone, which is a specific level for diamonds compared to other stones. But for this particular machine, the sensitivity isn’t high enough, which means that the machine will much more quickly declare a stone a diamond than a more high-tech counterpart pen tester would, and thus in the end have false positive results for stones that are not diamonds but have a thermal conductivity close to it.

On the other hand, there can be issues of false negatives on some pen testers as well, which we will segue into now. We deal and have dealt with many different diamonds over the years, and while we prefer to have all pieces with full lab reports, we always double-check with an in-house test of the stone. In doing so, we have realized that at times, there can also be issues of false negatives, specifically when dealing with lab diamonds, both the CVD and HPHT types. This false negative would only be on pen testers, where the stone would show as moissanite instead of a diamond. To clarify why this can happen, please keep reading:

CVD (Chemical Vapor Deposition) and HPHT (High Pressure High Temperature) lab-grown diamonds can sometimes test as moissanite on pen testers due to the similar thermal and electrical conductivity properties between these materials. Here are some detailed reasons:

1. Thermal Conductivity:
• Both diamonds (natural and lab-grown) and moissanite have high thermal conductivity. Pen testers, which are commonly used to distinguish diamonds from other gemstones, often rely on measuring thermal conductivity. Since moissanite's thermal conductivity is very close to that of diamond, the tester might misidentify a lab-grown diamond as moissanite.
2. Electrical Conductivity:
• Some pen testers also use electrical conductivity to differentiate gemstones. Moissanite exhibits electrical conductivity properties that can sometimes overlap with those of lab-grown diamonds, especially CVD diamonds, which may have trace amounts of impurities (like nitrogen or boron) that affect their electrical properties. This can lead to incorrect readings. These impurities occur from the manufacturing of this type of lab diamond.
3. Instrument Sensitivity and Calibration:
• The sensitivity and calibration of pen testers can vary. In some cases, the testers may not be finely tuned to distinguish between the subtle differences in properties between diamonds and moissanite. This lack of precision can result in lab-grown diamonds being misidentified.

Conclusion:

Basically, what we are trying to say is not to take the first reading from a pen tester as a final result of a stone and to always make sure that you have done proper thorough testing of the stone, which should always include at least one test of the stone in a box tester. This is because the box testers are much less likely to have issues with false positives or negatives.

It goes without saying that it should also always be a requirement to have some sort of stone report when it comes to natural and lab diamonds, as that is a surefire result, given the amount of technology the most well-known labs have nowadays.