Diamond Tester vs Diamond Screening Device

Overview

A diamond tester tells you whether a stone is diamond material; a diamond screening device tells you whether that diamond is natural or lab-grown. That one difference is why a tester cannot flag a lab-grown stone, and it is what separates the three commercial tiers of diamond detecting equipment on the market today. Every jeweler assumes they know what a diamond tester does; fewer realize that "tester" now covers two genuinely different categories of tool, and that confusing the tiers is where real risk creeps into a jewelry business. This guide walks through all three: the standard diamond tester, a newer generation of combination testers, and the true diamond screening device, also called a diamond screener or diamond verification device, what each one actually measures, and where each one runs into trouble with lab-grown diamonds, diamond simulants, moissanite, and cubic zirconia (CZ).

Diamond Screener, Diamond Screening Device, Diamond Verification Device: Same Instrument, Three Names

Before going further, one point of terminology worth clearing up. In the trade, "diamond screener," "diamond screening device," and "diamond verification device" all refer to the same category of instrument, the top tier covered below, built to determine whether a diamond is natural or lab-grown. They are used somewhat interchangeably depending on the supplier or region. A "diamond tester," by contrast, is a different and older category of tool, built to answer a narrower question: is this even diamond material at all. Keeping that distinction straight is the difference between buying the right instrument for the risk a business actually faces and assuming any handheld device covers it.

The Three Commercial Tiers of Diamond Detecting Technology

At the entry level is the standard diamond tester, a pocket tool that answers a single question: is this stone diamond material, or a diamond simulant like cubic zirconia? In the middle is a newer generation of combination testers, still handheld, still probe-based, but built to add a partial signal about a stone's origin on top of the material check. At the top is the diamond screening device, also marketed as a diamond screener or diamond verification device, a benchtop or portable instrument built specifically to determine whether a diamond formed naturally underground or was grown in a lab. It is only this top tier that is actually designed to answer that question with any real confidence.

The distance between these tiers is not just price. It is a difference in what physical principle each one relies on, and that difference determines what each one can and cannot reliably catch.

Tier 1: The Diamond Tester (Thermal and Electrical Conductivity)

A standard diamond tester relies on thermal conductivity, electrical conductivity, or a combination of both. A probe touches the stone, and diamond, which conducts heat unusually well compared to most simulants, pulls warmth away from the tip fast enough for the meter to register a "diamond" reading. Electrical conductivity testers work the same way, measuring how quickly a small current passes through the stone instead of heat.

These are fast, inexpensive, single-purpose tools, and for the job they were built to do, they do it well.

Can a Diamond Tester Detect Moissanite or Cubic Zirconia (CZ)?

Against cubic zirconia, yes, reliably. CZ conducts heat and electricity poorly compared to diamond, and a basic thermal probe catches that difference easily. Moissanite is the well-known exception: it conducts heat as efficiently as diamond, sometimes more so, so a thermal-only tester will read a moissanite stone as diamond nearly every time. Combined thermal and electrical testers were built to close that specific gap, since moissanite and diamond behave differently under an electrical current, and a good combination diamond tester will correctly separate diamond from moissanite in most cases.

The Diamond Tester's Blind Spot: Lab-Grown Diamonds

What none of this touches is origin. Natural and lab-grown diamonds are the same material, carbon crystallized in the same cubic lattice, and they conduct heat and electricity almost identically. A stone grown in a lab last month reads "diamond" with exactly the same confidence as a stone that formed a billion years underground. Combined testers introduce their own narrower blind spot too: HPHT lab-grown diamonds can retain trace metallic catalyst material, and boron-doped stones, whether natural or lab-grown fancy blue diamonds, conduct electricity in a way that can misread as moissanite rather than diamond. A diamond tester is doing exactly the job it was designed for. That job was never diamond identification of natural versus lab-grown origin.

Tier 2: The New Generation of Combination Testers

A newer class of handheld testers has entered the market that tries to go a step further. These are dual-probe devices: one tip still performs the conventional thermal or electrical conductivity check, and a second tip shines long-wave ultraviolet light, commonly around 365nm, at the stone to see whether it fluoresces. That second tip is a real step forward from a standard diamond tester, because fluorescence under long-wave UV is one of the actual signals used to help separate natural from lab-grown diamonds. For the first time, a pocket tool is attempting to speak to origin, not just material identity.

It is still a meaningfully thinner read than what a true diamond screening device captures, for a few concrete reasons. A single glance under one UV wavelength returns only fluorescence color. It does not capture phosphorescence, whether and how a stone continues to glow after the UV source is switched off, which is the other half of the diagnostic pair that helps separate HPHT and CVD signatures from natural diamonds. It is also a qualitative, by-eye read taken in ambient light through a small tip, not a timed, color-calibrated image captured in a controlled dark chamber. And the physics itself works against a simple glow check: roughly a quarter to a third of natural diamonds fluoresce weakly or not at all under long-wave UV, and CVD lab-growns, the type that most needs catching, are frequently weak or non-fluorescent as well. That means a "no glow" reading on this kind of device is genuinely ambiguous rather than reassuring, and it is ambiguous in exactly the case that matters most.

These weaknesses show up as a real operational problem in day-to-day use, not just a theoretical one. The UV output on a pocket probe is inherently weak compared to the calibrated illumination inside a benchtop screening device, so the reading is far more sensitive to conditions the operator cannot fully control. A stone that is not perfectly clean, carrying oil, dust, or handling residue on the table, will scatter or dampen a weak UV signal enough to produce an unclear or misleading glow. The angle at which the probe meets the stone matters just as much: a fluorescence read taken slightly off-axis from a fixed, low-power UV source can look markedly different from one taken straight on, even on the same stone. Cut shape compounds both problems. Round brilliants return light in a fairly predictable, well-understood pattern, but fancy shapes, princess, emerald, marquise, pear, and others, have different facet geometries and pavilion angles that change how fluorescence is visible through a small viewing window. In practice, this combination, weak UV output, stone cleanliness, probe angle, and cut shape, is what drives combination testers toward a high referral rate in real-world conditions, and a device that refers a large share of stones regardless of what it is looking at stops being a useful triage tool and starts being a source of confusion for the operator relying on it.

Treat a combination diamond tester for what it is: a meaningful upgrade over a standard tester, and a legitimate first-pass triage tool when conditions are controlled, but an instrument whose real-world referral rate is highly sensitive to stone cleanliness, probe angle, and cut shape, not a substitute for imaged fluorescence paired with phosphorescence, and not the same category of instrument as a true diamond screening device.

The Limitation Every Diamond Tester Shares: Contact

Standard testers and combination testers share a structural limitation that has nothing to do with which physical property they measure. Both work by physically touching a probe tip to the stone. That works fine on a full-size, accessible loose stone sitting on a bench. It breaks down in two situations jewelers deal with constantly.

The first is melee. On a small stone, there is often not enough clean surface area for an isolated probe contact, and the probe frequently touches adjacent prongs or metal at the same time, contaminating a thermal or electrical reading and, on a combination tester, potentially skewing the UV read as well. The second is mounted jewelry generally, where getting a clean, perpendicular touch on every stone in a cluster or pave setting is slow at best, and on some stones physically impossible without removing the piece from its setting entirely.

There is also a workflow cost that follows directly from being a contact instrument. Because every reading requires physically touching that one stone, testing a parcel or a tray of loose diamonds means testing every stone one at a time, in sequence, resetting for a fresh contact and a fresh reading each time. There is no way around that with any probe-based diamond tester, regardless of which tier it belongs to.

Tier 3: The Diamond Screening Device (Diamond Screener, Diamond Verification Device)

A diamond screening device works on a different physical principle entirely, optical rather than thermal or electrical, and it is built around cameras and controlled illumination rather than a physical probe. Instead of touching the stone, it images it, capturing how it reacts to light under controlled conditions. Because natural and lab-grown diamonds form under very different pressure, temperature, and growth conditions despite being chemically identical carbon, those different growth histories leave behind different optical fingerprints that imaging can capture with far more precision than a handheld glance.

Being contactless and camera-based solves both problems that come with a probe-based diamond tester. A camera does not need to touch a stone to read it, so a small melee stone or a diamond set close to a prong is not a contact problem the way it is for a probe. And because imaging captures an entire field of view rather than one point of contact, a diamond screening device can analyze a full tray of loose stones, or a full piece of jewelry, in a single pass, rather than requiring the operator to test each stone individually. This is also what makes a diamond screening device the right instrument for diamond identification at scale, sorting parcels, verifying inventory, or clearing pieces before certification, rather than one-off spot checks.

The REVEAL Approach: Multi-View Imaging

JTR's REVEAL Diamond Detector 3S & 2S apply this optical, contactless approach directly, and the two devices illuminate a stone differently to get there. The REVEAL Diamond Detector 2S examines a stone under Deep UV, capturing fluorescence and phosphorescence under that single wavelength band. The REVEAL Diamond Detector 3S combines Deep UV and Long UV illumination, collecting fluorescence and phosphorescence data across both wavelength bands rather than one. That second data set gives the device more to work with on stones whose reaction under Deep UV alone would otherwise sit in a gray area, which is what lowers the referral rate on the REVEAL Diamond Detector 3S compared to the REVEAL Diamond Detector 2S.

Each device captures four diagnostic views of a stone, Daylight, Fluorescence, Phosphorescence, and Result, on both loose diamonds and finished jewelry, imaged rather than probed. On the REVEAL Diamond Detector 2S, the operator reads the fluorescence and phosphorescence color patterns directly, referencing known signatures (blue fluorescence for natural diamond, intense turquoise fluorescence with turquoise phosphorescence as a signal to refer a potential HPHT lab-grown stone, and so on). The REVEAL Diamond Detector 3Sadds auto-detection, an exclusive capability that classifies each stone as Natural, Potential Lab-Grown, or Potential Simulant automatically, drawing on the combined Deep UV and Long UV data, while still showing the operator the raw fluorescence and phosphorescence images behind that verdict, so human judgment stays in the loop rather than being replaced by it. Auto-detection on the REVEAL Diamond Detector 3S analyzes up to 40 loose stones in a single batch, imaged together rather than tested one by one.

That Potential Simulant category is not a minor footnote. Moissanite and cubic zirconia (CZ) both fluoresce and phosphoresce differently from diamond, so the same Deep UV and Long UV imaging that separates natural from lab-grown also catches these diamond simulants, on both the REVEAL Diamond Detector 2S and REVEAL Diamond Detector 3S. That is the real advantage of an advanced diamond screening device over a single-purpose diamond tester, one imaging pass answers the material question and the origin question together, rather than needing a separate tool for each.

This is the kind of claim that should not be taken on a manufacturer's word alone. The REVEAL Diamond Detector 2S has been independently evaluated under the Natural Diamond Council's ASSURE 2.0 protocol, a testing standard run with independent laboratories including GIA and HRD Antwerp, using novice operators rather than manufacturer-trained staff. The published result: a 0.0% Diamond False Positive Rate across every sample set tested, primary loose, smalls, and mounted stones alike, meaning no lab-grown or synthetic diamond in the sample set was ever missed and cleared as a confirmed natural diamond. In practical terms, that is a verified 100% lab-grown detection rate for the REVEAL Diamond Detector 2S, checked by a neutral third party rather than claimed internally. The REVEAL Diamond Detector 3S is built on the same standard: both devices are measured at a 0.0% Diamond False Positive Rate, meaning neither one has let a lab-grown or synthetic diamond pass through as a confirmed natural stone.

Diamond Tester vs. Combination Tester vs. Diamond Screening Device: Side by Side

Why the Trade Increasingly Needs a Real Diamond Screening Device

None of these tiers make the others obsolete on their own, but relying on a diamond tester or combination tester as a stand-in for real diamond screening is where risk enters a business. Growth methods keep evolving, catalyst formulas change, doping techniques shift, and any probe-based technology, tested one stone at a time under a single physical principle, eventually meets a stone it was not built to catch. That is a harder problem for melee and pave work specifically, where a probe cannot even get a clean, isolated read in the first place.

It is also worth knowing that some of the best-known names in diamond detection require an active subscription just to operate the hardware you already paid for, not merely to unlock extra cloud features. REVEAL Diamond Detector 3S & 2S never require a subscription for core diamond screening, auto-detection, or lifetime software updates. That is a deliberate positioning choice: the diamond screening device you buy should keep working for as long as you own it.

Frequently Asked Questions About Diamond Testers, Diamond Simulants, and Diamond Identification

What is the difference between a diamond tester and a diamond screening device?

A diamond tester checks whether a stone is diamond material at all, separating diamond from diamond simulants like cubic zirconia or moissanite, using thermal or electrical conductivity. A diamond screening device, also called a diamond screener or diamond verification device, answers a different question: whether a diamond that has already been confirmed as diamond material is natural or lab-grown, using optical imaging rather than a physical probe.

Can a diamond tester detect moissanite or cubic zirconia (CZ)?

A diamond tester catches cubic zirconia reliably, since CZ conducts heat and electricity very differently from diamond. Moissanite is harder: a thermal-only tester frequently misreads moissanite as diamond, since the two conduct heat similarly. A combined thermal and electrical diamond tester, or a combination tester with an added UV probe, catches moissanite in most cases.

What is the difference between a diamond simulant and a lab-grown diamond?

A diamond simulant, such as moissanite, cubic zirconia, or glass, is a different material entirely that only resembles diamond visually. A lab-grown diamond is actual diamond material, real carbon in the same crystal structure as a natural diamond, grown in a laboratory rather than formed underground. This is exactly why a diamond tester cannot tell the two apart: a lab-grown diamond passes every conductivity check a natural diamond does, because it is chemically and structurally diamond.

Does a diamond tester perform diamond identification, or just diamond detection?

A standard diamond tester performs basic detection: diamond versus simulant. Full diamond identification, confirming natural origin versus lab-grown, requires the optical technology found in a diamond screening device, or in some cases, laboratory-grade spectroscopy.

Why do combination diamond testers refer so many stones in real-world use?

The long-wave UV output on a handheld combination tester is weak compared to the calibrated illumination inside a benchtop diamond screening device, so the reading is highly sensitive to conditions the operator cannot fully control. A stone that is not perfectly clean, the wrong probe angle, or a fancy shape with an unfamiliar facet pattern can all produce an unclear glow, and the device refers the stone rather than returning a confident result. In practice, this tends to push combination testers toward a high referral rate, which can be confusing for an operator expecting a clear answer.

Do diamond screening devices also detect diamond simulants like CZ and moissanite?

Advanced diamond screening devices, including the REVEAL Diamond Detector 3S & 2S, detect diamond simulants as well as lab-grown diamonds. Moissanite and cubic zirconia (CZ) both fluoresce and phosphoresce differently from diamond, so the same imaging that separates natural diamonds from lab-grown ones also flags these simulants, all in the same pass.

Is a diamond screener the same thing as a diamond verification device?

Yes. "Diamond screener," "diamond screening device," and "diamond verification device" are used interchangeably in the trade to describe the same category of instrument, built to determine whether a diamond is natural or lab-grown.

Do diamond screening devices require a subscription to operate?

Not all of them, though some well-known instruments do require an active subscription just to power on and screen. REVEAL Diamond Detector 3S & 2S never require a subscription for core screening, auto-detection, or lifetime software updates.

The Takeaway

A diamond tester, a combination tester, and a diamond screening device are three different tools solving three different problems, and moving up a tier is not a matter of buying a fancier version of the same thing. A standard diamond tester is a fast, reliable confirmation that a stone is diamond material rather than a diamond simulant like glass or cubic zirconia. A combination tester adds a genuine but limited first read on origin, useful as a step up, not as a final answer. A diamond screening device, whether called a diamond screener or a diamond verification device, is the instrument built to answer the question that actually protects a jewelry business today, unknowingly selling an undisclosed lab-grown diamond as natural, and it is the only one of the three built to handle melee, pave, and full trays of stones without the contact limitations every probe-based diamond tester shares. For any point of sale, workshop, or lab handling natural diamonds, knowing which tier is in your hand, and which question it can actually answer, is where diamond verification starts.