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Do SI Diamonds Pass Diamond Tester?

Do SI Diamonds Pass Diamond Tester?

We’ve all heard about diamonds failing (or passing) diamond testing, but why is that and do all diamonds pass the diamond tester? Well, today we’re taking a look at do SI, or slightly included diamonds pass diamond tester?

It’s interesting to notice that SI is a sign of diamond clarity, and doesn’t indicate the diamond’s authenticity. Slightly included diamonds are real diamonds that have been graded by an organization accredited for that sort of grading and have been given one of the lowest grades for clarity – Slightly Included (SI).

Now, since SI diamonds do pass a diamond test it’s time to see why they pass it, what kinds of diamond tests they pass, and a ton of interesting information closely related to this topic. Without any further ado, let’s jump in and see what we have in store for you!

What Are SI (Slightly Included) Diamonds?

Before we go and talk about diamond testing and passing those tests, let’s take a look at what slightly included diamonds exactly are.

Slightly included (or SI) diamonds are diamonds that have been graded for their clarity level by an organization such as GIA, IGI, AGS, etc…These organizations grade diamonds for their color, and their clarity, and weigh them so there’s an exact carat number on the certificate.

SI or slightly included diamonds are diamonds that have a low grade of clarity since it’s only the second-lowest on the scale. When we’re at the topic of the scale, let’s take a look at what grades can diamond get on that scale of clarity:

Now, you may have noticed that the diamond that we’re interested in, the slightly included ones, are ranked pretty low, and that’s because their level of clarity isn’t satisfactory enough so they can be graded with a higher grade.

That doesn’t mean that these diamonds aren’t authentic, but it only means that the diamond they were made from formed with specific characteristics that didn’t make it clear enough. In other words, slightly included diamonds are diamonds that have imperfections that impact their level of clarity.

The thing about SI diamonds is that they’ll give you the best bang for your buck. These diamonds are some of the most popular since their imperfections when it comes to clarity are hard to see but have a lower price tag than diamonds that have a VS or a VVS grade of clarity.

All-in-all, these are some of the most popular diamonds. Yes, they do have clarity-related imperfections, but they’re perfectly viable if you’re searching for the best price-to-quality ratio.

SI (Slightly Included) Diamonds – Are They Fake?

These diamonds aren’t fake. Only real diamonds, regardless of if they’re lab-grown or natural, can be graded for their clarity by serious and world-renowned organizations. But why do people think these diamonds are fake?

This misconception comes from the diamond industry’s marketing side, which likes for you to think that the only viable diamonds are those with the best clarity, and often color, grade. Slightly included diamonds are genuine, and there’s no need to doubt their authenticity, especially if an organization such as GIA has graded them.

SI diamonds, as we’ve said, are some of the most popular diamonds out there since they give you the best price-to-quality ratio, and since people like to have pretty things that don’t cost much – SI diamonds are often their first choice!

There is one problem with SI diamonds though and that’s the fact that diamond cons often make their fake diamonds appear as SI diamonds since that’s the most believable diamond they can make and sell easily.

Since the demand for SI diamonds is the highest out of all clarity grades, people who make fake diamonds tend to make them as close to SI diamonds as possible to sell them more easily.

It doesn’t matter that they’ll make less money per diamond sold, their goal is to sell as many diamonds as possible, and there are not many people around that buy FL grade diamonds from “shady diamond dealers”.

Considering that, now you’re getting the picture of why people often see SI diamonds as fake – most fake diamonds are presented with the SI clarity grade.

Diamond Certificates

Diamond certificates are the only legitimate way of validating your diamonds. Every serious jewelry store or diamond dealer tends to give you a valid certificate for the diamond you’ve just bought.

But, there are some instances where you’ll have to get a certificate for your diamond by yourself. That means that you’ll have to go and get your diamond certified by an organization renowned and known for its accuracy and credibility.

Depending on which part of the world you’re from, you can go with multiple different choices when it comes to diamond certification organizations.

In North America, the most well-known and praised organization for diamond validation is the Gemological Institute of America or GIA. GIA handles a big chunk of diamond certification business in the US and is probably the safest option if you’re from that part of the world. If you’re from Europe, you’ll probably have some other options to consider since it’s hard to ship a diamond to the US.

Asia and Africa are pretty much the same deal, you’re better off to go with the most well-known gemology institute or organization that is known for certified diamonds. Regardless of which organization or institute you go with, it’s important to know that you’ll get a few “markers” or grades for your diamond.

First is the color grade, the second is the clarity grade (in which we’re currently interested), and the weight of your diamond in carats. The color grade is not as important as the clarity grade at the moment, so we won’t spend any time on it.

But instead, let’s take a look at the clarity grade. Every diamond has its clarity grade, and once the clarity grade has been given, there’s no turning back meaning that you can get your diamond to be graded higher for its clarity than it initially was.

This clarity grade is closely tied with the list of clarity grades that we showed you earlier, and every diamond can be graded by one of those grades.

Learn More: Diamond Color Vs. Clarity: What’s More Important?

Thermal Diamond Testing

There are two ways to test your diamond’s authenticity, and that’s diamond testing done with thermal conductivity, and diamond testing done with electrical conductivity.

First, let’s take a look at thermal conductivity-based diamond testing since this is the most widely used and known way of testing diamonds for authenticity.

If some of you are thinking about diamond testers that are black and have a small screen with red, orange, and green or blue indicators for authenticity, you’re thinking of primarily thermal conductivity-based testers!

But, electrical conductivity-based testers also look similar, so you’re not far off if you thought of these types of diamond testers. But, we digress – let’s take a look at how the thermal-conducting diamond testers work.

First of all, it’s important that you know that diamonds are some of the best thermal conductors you can find, alongside graphite and graphene. This means that diamonds should conduct heat quite well, and that’s what is tested with thermal-based diamond testers.

The process behind this diamond tester is quite simple, and it includes sending heat into the stone and measuring how fast the stone conducts that heat. If the stone conducts heat fast enough, the stone tests positive, but if it needs significantly more time, the tester will show you that the rock you’re testing is not a diamond.

A method such as this is suitable since all diamonds (both lab-grown and natural) have the same characteristics when it comes to thermal conductivity. Otherwise, if a tested gemstone doesn’t show those specific heat-conducting characteristics, it’s considered a fake.

SI diamonds are as good heat conductors as any other genuine diamonds due to their strong covalent bonds between carbon atoms in a diamond crystal.

Electrical Diamond Testing

Electrical conductivity-based diamond testers are similar, working on very similar models and testing diamonds similarly. The electrical resistivity of most diamonds is on the order of 1011 to 1018 Ω·m and that’s what we’re looking for when testing a diamond with this method.

SI diamonds pass both thermal and electrical conductivity tests since they’re genuine diamonds. Regardless of their clarity-based imperfections, these diamonds conduct electricity as well as other diamonds that may be graded with VSS or FL clarity grades, and there’s no mistake about it.

As we’ve said, electrical conductivity testing works on a similar principle to the one used in thermal conductivity diamond testing. A device used to measure the level of electrical conductivity of a diamond (including the SI diamonds) lets out an electrical impulse that travels through a diamond that’s touching it.

Electrical conductivity-based diamond testers measure the amount and speed through which electricity travels through the gem in question, and that’s all there is to it. If the electrical conductivity is within the boundaries we’ve mentioned earlier (1011 to 1018 Ω·m), then it’s considered to test positive and declared genuine.

Both of these devices used to authenticate diamonds are easy to buy, set up, and use – so anybody that takes a bit of interest in them can learn how to use them by themselves. Some people tend to learn this and carry their own diamond testers around when they’re in the market for a diamond or two.

Electrical conductivity testers may be more complicated to set up, but it’s not impossible with some time and patience!

Related Read:

Why Do SI (Slightly Included) Diamonds Pass Diamond Testing?

As we’ve said earlier, diamonds graded with SI clarity level are genuine diamonds, which means they aren’t any different from VS, VVS, or FL diamonds (except for clarity level) when it comes to their properties.

All diamonds are amazing thermal conductors and quite good conductors of electricity, which makes them perfectly viable for a positive diamond test.

Genuine diamonds, regardless of their color or clarity grade, have the same chemical characteristics, and that’s what is tested with diamond testers, so that means that SI diamonds don’t have any problems passing a diamond authenticity test.

Of course, when we’re talking about fake diamonds that are made to look like slightly included diamonds won’t pass that test, but not because of their clarity level. They won’t pass the test because of their chemical characteristics or their thermal and electric conductivity characteristics, to be more precise.


As you’ve seen throughout the article, diamonds with a clarity grade of SI (slightly included) are genuine diamonds. Thus, the answer to the question of “Do SI diamonds pass diamond tester?” is positive without any doubt.

Electric conductivity and thermal conductivity diamond testers show a positive result for SI diamonds without mistake, and often the diamonds that are tested don’t have a clarity grade yet, so that goes to show you how irrelevant it is.

So, if you have a SI diamond, don’t worry about it passing the diamond tester since it most definitely will!