How to Use Diamond Selector 2: how to use diamond selector 2 in testing (2026)

It's always exciting to unbox a new tool, but with a Diamond Selector 2, accuracy hinges on what you do before your first test. This initial setup is a non-negotiable checklist that involves powering it on correctly, letting it warm up, and calibrating it for the environment. If you skip this, you might as well be flipping a coin.

Your First Test: Unboxing and Calibrating the Diamond Selector 2

So, you're ready to start testing. Before you touch the probe to that new bracelet or a find from an estate sale, a little prep work is in order. Think of it like tuning an instrument before a performance—it’s the only way to ensure what you hear (or in this case, see) is the truth. Honestly, rushing this part is the biggest mistake I see new users make.

Power and Warm-Up

First things first, let's talk about power. Your diamond selector measures thermal conductivity, and it needs a clean, stable electrical current to do its job. This is why you should always use a fresh, high-quality 9V battery. A cheap or dying battery can cause voltage dips that throw off the readings, a common reason real diamonds might falsely test as simulants.

With a fresh battery installed, switch the device on. You’ll immediately see the "POWER" light, and usually a "WAIT" or "WARM UP" light will glow. Don't test anything yet. This is a crucial waiting period. The sensitive probe tip needs about 20-30 seconds to reach its precise operating temperature. You're good to go only when the "READY" light turns green.

Initial Calibration for Peak Accuracy

If you want to know how to use a Diamond Selector 2 and trust its results, you have to calibrate it. Every single time. This step tunes the tester’s sensitivity to the room's temperature and the general size of the stone you're about to test.

Pro Tip: Always calibrate using a known, real diamond. If you don't own one, many testers include a small test stone for this purpose. Using a real diamond as your baseline tells the machine exactly what it should be looking for.

Here’s the simple process I follow:

• Set the Starting Level: Turn the volume dial until only one or two green lights are showing on the meter. This is your baseline.
• Touch the Known Diamond: Press the probe tip firmly against your known diamond. Make sure the contact is perpendicular—straight on, not at an angle.
• Adjust for Diamond: While holding the probe on the stone, slowly turn the dial clockwise. Keep going until the lights climb into the red "DIAMOND" area and you hear a steady beep.

That’s it. Your tester is now calibrated.

Just remember, a quick re-calibration is a good idea if you move to a much warmer or colder room. The same goes if you switch from testing tiny accent stones to a large solitaire. This tiny adjustment is what separates someone who’s just guessing from someone who can truly rely on their tool.

Getting the Technique Right Every Time

Once your Diamond Selector 2 is warmed up and calibrated, you’re ready to test. The next few moments are crucial—how you handle the stone and the tester will make the difference between a reliable reading and a total guess.

The single biggest reason people get false readings isn't a broken tester; it’s a dirty stone. Before you do anything else, make sure the gem is clean, dry, and at room temperature. The selector works by measuring heat conductivity, and any residue can throw it off completely.

Prepping the Stone and Setting

Lotions, fingerprints, and everyday grime create a thin, insulating film on the stone's surface. This film slows down the heat transfer from the probe, which can easily make a genuine diamond read as something else. Always give the stone a quick, thorough wipe with a clean, lint-free cloth right before you test.

Next, you need to hold the piece of jewelry correctly. Your body is part of the electrical circuit the tester needs to function, so your hand must be touching the metal part of the piece. If you’re testing a ring, just grip the metal band. For a pendant, make sure you're holding the chain or the metal setting around the stone.

A Pro Tip: Testing a small stone in a big, heavy setting like an iced-out Cuban link bracelet can be a pain. You have to make sure you’re holding the metal links with one hand while you touch the probe to the stone with the other. If you just hold the tester and not the jewelry, you won't complete the circuit, and the tool won't give you any reading at all.

How to Use the Probe for an Accurate Test

This is where your technique really matters. How you apply the probe is everything.

• First, hold the tester like a pen. Make sure your fingers are touching the silver, conductive plate on the back or side of the device. This is essential for completing the circuit.

• Bring the probe’s tip straight down onto the stone. You want to aim for the largest, flattest surface you can find, which is usually the table (the flat top facet).

• Gently but firmly press the spring-loaded tip onto the gem so it’s perfectly perpendicular (a 90-degree angle) to the surface. You'll see the tip retract a little bit—that's what you want. Hold it steady for a couple of seconds until the tester beeps and the LED lights settle on a final reading.

Coming in at an angle is a common mistake that causes the probe to slip or make poor contact, giving you a bad reading. It’s all about creating a clean, direct path for the device to do its job. For a deeper dive into identifying real diamonds beyond just using a tester, check out our guide on how to tell if diamonds are real.

Interpreting Your Diamond Selector 2 Results

The lights and beeps are the tester's language. This table breaks down what those signals mean so you can quickly understand what you're looking at.

Material Tested	Diamond Selector 2 Indication	What It Means
Diamond	Full or near-full red lights and a continuous beep.	The stone is an excellent thermal conductor, consistent with a diamond.
Moissanite	Full or near-full red lights and a continuous beep.	Moissanite is also an excellent thermal conductor and will falsely test as a diamond on this device.
Cubic Zirconia (CZ)	No lights or only one or two green lights illuminate. No beep.	The stone is a poor thermal conductor, indicating it is likely a simulant like CZ.
Glass / Crystal	No lights illuminate. No beep.	The material has very low thermal conductivity, ruling out diamond.
Metal Setting	A continuous, loud "chatter" or intermittent buzzing sound.	You've accidentally touched the metal prongs or bezel instead of the stone. Reposition the probe and re-test.

Understanding these results is the final piece of the puzzle. Just remember, if your tester lights up for "diamond," your job isn't quite done—you still need to figure out if it's a diamond or its tricky look-alike, moissanite.

The Moissanite Blind Spot: Why One Test Isn't Enough

You've done everything by the book. You cleaned the stone, fired up your Diamond Selector 2, and touched the probe to the surface. Instantly, the lights race into the red, and the machine lets out a steady, confident beep. It's a diamond, right?

Not so fast. This is the exact moment where so many shoppers and new collectors get a false sense of security. While a thermal tester like the Diamond Selector 2 is fantastic for weeding out common fakes like glass or cubic zirconia, it has one critical blind spot: moissanite. This incredibly popular diamond alternative will fool a basic thermal tester every single time.

Think of this flowchart as your road map for getting an accurate result. It's not just about getting a positive reading, but knowing what to do next.

Notice how a "Diamond" result isn't the end of the line? It's a crucial decision point that demands a follow-up step.

Why Your Thermal Tester Gets Fooled

The Diamond Selector 2 operates on a simple principle: thermal conductivity. It measures how quickly a material pulls heat away from its sensitive probe tip. Diamonds are legendary thermal conductors, siphoning heat away almost instantly. That rapid heat transfer is what triggers the "diamond" reading on your device.

Here's the catch: moissanite is also a highly effective thermal conductor. While its properties aren't identical to a diamond's, they are close enough to trick the tester into giving the exact same positive result. It’s a classic case of mistaken identity. If you want to learn more about this remarkable stone, we have a complete guide covering what moissanite is and how it stacks up against diamond.

Among professional jewelers and serious hobbyists, a positive result from a Diamond Selector 2 is never the final word. It's simply step one. Relying on that initial thermal test alone is the quickest way to overpay for a stone, thinking you’ve bought a diamond when you actually have moissanite.

The Two-Test Method Professionals Use

So, how do you solve the moissanite puzzle? You have to test for a property where the two stones are completely different: electrical conductivity.

It’s a simple distinction. While both stones conduct heat well, their electrical properties are worlds apart.

• Diamonds are electrical insulators. They do not conduct electricity.
• Moissanite, on the other hand, does conduct electricity.

This is the key that unlocks a definitive identification. To measure this, you need a second tool—a moissanite tester or a combination multi-tester that checks for both thermal and electrical conductivity.

The workflow used by the pros is straightforward. First, you use the Diamond Selector 2 as a screener. If the reading is low (in the glass or metal range), you know it’s not a diamond or moissanite. Your work is done.

But if the thermal tester screams "diamond," you're not finished. You immediately bring in the moissanite tester for the final verdict. Test the exact same spot on the stone. If that second device lights up or beeps, you've confirmed it's moissanite. If it stays completely silent, you can finally relax—you're holding a real diamond.

Maintaining Accuracy With Proper Care and Troubleshooting

Let's be real: a testing tool is only as good as the care you give it. To keep your Diamond Selector 2 giving you results you can trust, a little bit of maintenance goes a very long way. Just like any precise instrument, its accuracy can drift over time from dirt, oils, or just plain old wear and tear.

The single most important part to keep clean is the retractable probe tip. After just a few tests, it can pick up a microscopic film of residue from the stones or even oils from your skin. This tiny layer acts as an insulator and will absolutely throw off your readings. Keeping that tip pristine isn't optional—it's essential.

Of course, keeping your tester in top shape goes hand-in-hand with caring for your jewelry. To learn how the pros keep their pieces sparkling, check out our guide on how to clean diamond jewelry.

Essential Care and Upkeep

Proper maintenance is surprisingly quick and makes all the difference. Your main focus should always be on that probe tip and making sure your testing surface is clean.

• Clean the Probe Tip: I make it a habit to gently wipe the probe tip with a soft, lint-free cloth after every 5-10 tests. If you're getting flaky results or see any visible buildup, a dab of isopropyl alcohol on the cloth will cut right through it. Just be sure the tip is completely dry before you use it again.
• Wipe Down the Body: A quick wipe-down with a dry cloth keeps the tester's body and the metal contact plate clean. This stops grime from getting on your hands and then onto the stones you’re about to test.
• Store It Right: When you're done, put the Diamond Selector 2 back in its case. This is crucial for protecting the sensitive probe from dust or an accidental knock. And try to avoid leaving it in your car or anywhere with big temperature swings, which can mess with calibration and drain the battery.

Common Problems and Quick Fixes

Even with the best care, you’ll occasionally run into a snag. Don't immediately assume the tester is broken—most issues are simple fixes.

What if the "READY" light won't come on? Nine times out of ten, this is a power problem. First, pop in a fresh battery and make sure it's seated correctly. If that doesn't work, take a look at the battery contacts inside the compartment. Sometimes they get a little dirty; a quick polish with a dry cloth or even a pencil eraser can fix the connection.

I’ve had people get frustrated when a stone they know is a diamond gives them inconsistent readings. If you've already cleaned the stone and the probe tip, the next thing to do is re-calibrate. A significant change in room temperature can throw off the tester's sensitivity. A quick re-calibration resets its baseline and gets you back to accurate testing.

If the tester starts buzzing loudly the second you touch the stone, you probably hit the metal prongs of the setting by mistake. It happens. Just pull back and reposition the probe so it’s making solid contact only with the gemstone.

Following these simple tips will ensure that every time you pull out your Diamond Selector 2, you can be confident in the results it gives you.

Understanding Your Tester: Its Limits and When to Call a Pro

Think of your Diamond Selector 2 as an incredibly effective gatekeeper, not the final judge. It’s a fantastic tool for its specific job, but knowing its boundaries is just as important as knowing how to use it correctly. This is what separates a smart hobbyist from someone who makes a costly mistake.

For a collector or savvy shopper, its real power is in speed and convenience. It gives you that initial green light, quickly separating diamonds from the most common, low-cost fakes you'll encounter.

Where Your Tester Really Shines

Your Diamond Selector 2 is, at its heart, a high-speed screening tool. Its entire purpose is to check for high thermal conductivity—a key property that makes diamonds feel cold to the touch. This makes it a powerhouse for weeding out materials that don't conduct heat well.

It will instantly and accurately help you spot:

• Cubic Zirconia (CZ): The most widespread diamond simulant out there. It has very low thermal conductivity and won't stand a chance.
• Glass: Often used in costume jewelry, glass will not register on the tester’s scale.
• Crystal: Similar to glass, it won't fool the thermal probe.
• Other common fakes: Most materials you find passed off as diamonds will be flagged immediately.

This is invaluable when you're sorting through a big lot from an estate sale or checking a piece at a flea market. You can separate the definite "no's" from the "maybes" in seconds, saving yourself a ton of time.

The Diamond Selector 2 is your first-line verification tool. Its job is to confirm high thermal conductivity, which effectively rules out over 90% of common simulants. It gives you confidence as a collector but doesn't replace an expert's final word.

The Critical Part: What This Tester Cannot Do

Now for the catch. A positive "diamond" reading on this device is a great start, but it's not the end of the story. It doesn’t tell you a thing about the stone's quality or true identity.

Specifically, a Diamond Selector 2 cannot:

• Determine Diamond Quality: It provides zero information about the 4Cs—cut, color, clarity, or carat weight. A heavily included, cloudy industrial diamond will test the same as a flawless, investment-grade one.
• Distinguish Lab-Grown vs. Natural Diamonds: Lab-grown diamonds are chemically and physically identical to their natural counterparts. They share the same thermal properties, so your tester will correctly read both as "diamond" but can't tell you their origin.
• Differentiate Moissanite: This is the big one. As we covered, moissanite also has excellent thermal conductivity and will easily trick a thermal-only tester into a false positive.

So, when should you bring in a professional? Any time the stakes are high. For a high-value purchase, an insurance appraisal, or when you plan to sell a significant piece, nothing replaces professional verification. Get a formal grading report from a reputable gemological lab like the GIA (Gemological Institute of America).

Your tester gives you confidence in your day-to-day collecting. A gemologist provides certainty for your most important assets.

Common Questions (And Expert Answers) About Your Diamond Tester

Even when you feel you've got the hang of it, some questions always seem to pop up. Using a tool like the Diamond Selector 2 isn't just about following steps; it's about understanding why you're doing them. We've been there, so let's clear up some of the most common sticking points you'll likely encounter.

Think of this as the advice you'd get from a seasoned pro—practical answers for the real-world situations you'll face.

Can This Tester Spot a Lab-Grown Diamond?

Plain and simple: no, it can't. This is probably the most important limitation to understand. Lab-grown diamonds have the exact same chemical and physical properties as natural ones. Since the Diamond Selector 2 works by measuring thermal conductivity, it will read both as "diamond."

And that’s okay. This tool’s job is to tell you if a stone is a diamond or a fake (like cubic zirconia). It was never designed to determine a diamond's origin story. Distinguishing between a mined and a lab-created diamond requires highly specialized equipment you’d only find in a professional gem lab.

Why Do I Get Different Results on the Same Stone?

Getting jumpy or inconsistent readings is incredibly common when you're starting out. Before you blame the tester, check your process. It almost always comes down to one of three things.

• A Dirty Stone: Skin oils, dust, or lotion can act as an insulator and throw off the reading. Always give the stone a quick wipe with a clean, lint-free cloth first.
• A Contaminated Probe: The delicate tip of your tester can pick up residue. Gently wipe it on a clean surface after every few tests to keep it ready for an accurate reading.
• Your Technique: This is the big one. You need firm, consistent pressure. Make sure the probe is straight up and down (perpendicular) against a flat facet of the stone, and don't forget to maintain contact with the metal plate on the tester's body.

Most erratic readings aren't a sign of a faulty device. They're a sign that your technique needs a small tweak. A clean, consistent process is what separates a novice from a confident user.

Should I Calibrate Before Every Single Use?

Yes. Make it a non-negotiable habit. It takes less than 10 seconds and is the single best thing you can do to ensure reliable results. Calibration essentially "zeros out" the device for the current environment.

Think about it—the temperature in your room can change, and the tool itself warms up or cools down. By calibrating, you're giving the tester a correct baseline for the ambient temperature and the general size of the stones you're testing. It's a tiny step that pays off big in accuracy.

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