Can Sigma Metalytics Detect Tungsten-Core Gold?

By Telos Instruments Trading LLC · Exclusive Sigma Metalytics Distributor (UAE & GCC) · Al Uthman Building, Deira, Dubai, UAE

Quick answer: In most practical cases, yes, a Sigma Metalytics PMV is well suited to catching tungsten-core gold, but it should not be your only check. Tungsten has almost the same density as gold, which is why weighing a bar rarely exposes it. It has a noticeably different electrical resistivity, which is what the PMV measures, and the PMV Investor and PMV PRO add a density test as a second line of defence. Sigma Metalytics itself says the PMV should not be the sole means of identifying counterfeits, and recommends combining its readings with the bar’s specified weight and size. Telos Instruments, based in Deira, Dubai, supplies the PMV range and balances for this combined approach, and is the exclusive distributor of Sigma Metalytics in the UAE and GCC.

This guide explains why tungsten is a problem, how the PMV approaches it, what the limits are, and how to build a sensible verification routine.

Why Tungsten Cores Are Hard to Catch

Tungsten is used in counterfeit bars for a simple reason: its density (about 19.25 g/cm³) is almost identical to gold’s (about 19.3 g/cm³). A bar with a tungsten core and a gold exterior can match the weight and dimensions of a genuine bar closely, so the checks most buyers reach for first, a scale and a ruler, can pass.

Surface-only methods also struggle. If the outer layer is genuine gold, a test that reads only the surface sees gold.

That’s why verification needs to look beneath the surface, and why it needs more than one independent measurement.

How the PMV Approaches the Problem

Sigma Metalytics’ patented technology tests a sample’s characteristic resistivity. The sensor generates a small electromagnetic field and measures how the sample affects it. Genuine gold alloys have known resistivity profiles, and the device compares your sample with the profile for the alloy you select.

The density test: the PMV Investor and PMV PRO add a density test. Sensors measure the sample’s thickness, you enter its weight, and the device checks whether the dimensions fit the selected alloy’s density. Because resistivity and density are independent properties, a counterfeit has to satisfy both at once, which is much harder than satisfying either alone.

Through readings on bars: Sigma describes the PMV PRO‘s onboard sensors as testing all the way through samples up to 12.50 mm thick, and its optional External Bridge as performing resistivity and density tests through bars up to 45 mm thick, such as 100 oz silver and 400 oz gold bars.

What Sigma Metalytics Itself Says About Limits

It’s important to be straightforward about this, because it affects how you should use the device:

• Sigma states that the PMV should not be the sole means of identifying counterfeit coins and bars.
• It recommends using the specified weight and size of the coin or bar together with the resistivity measurement, because other materials can have the same resistivity as pure gold and could appear genuine on the PMV alone.
• The PMV reports the resistivity (and density, where supported) of the sample and whether it’s consistent with the selected alloy. It is a verification tool, not a laboratory assay.

In other words, the PMV is a powerful screening and verification layer, but you should still check weight, dimensions, and provenance.

Depth: How Far Beneath the Gold Can It See?

Buyers often ask how thick a gold layer can be before a tungsten core is hidden. Some resellers publish figures for specific models and wands (for example, claims about detecting tungsten at a few millimetres beneath gold cladding). Those figures depend on the model, the wand or sensor used, the bar’s size, and the sample’s construction, and they come from reseller descriptions rather than a universal guarantee.

Which PMV for Tungsten Detection?

A Practical Routine for Catching Tungsten-Core Bars

1. Check the seller and paperwork. Compare markings, serial numbers, and certificates with the bar.
2. Weigh the bar on a certified precision balance and compare with its specification.
3. Measure the dimensions against the specification for that bar type.
4. Run the PMV resistivity test with the correct alloy selected.
5. Run the density test (Investor or PRO), entering an accurate weight.
6. Test through packaging where applicable, so sealed bars stay sealed. This works through non-metal packaging.
7. Add an XRF check of the surface composition if useful, noting that XRF reads only the surface and near-surface layer.
8. Investigate any inconsistency before paying, and consider a specialist assay for very high-value or disputed bars.
9. Record everything.

What About XRF?

XRF analyzers, such as the Terra Scientific Aurora 900 and the handheld Pi900E, EulerX 900, and EulerX 900S, read the surface and near-surface composition. They’re excellent for jewellery, scrap, and plated base metals. For tungsten cores beneath a gold shell, they are not the primary tool, because they don’t see deep into a thick bar. XRF and PMV complement each other: XRF for the surface layer, PMV for what’s beneath.

Precision Balances: The Essential First Layer

Weight and dimensions are the first filter, and an accurate weight feeds the PMV’s density test. Telos Instruments supplies Adam Equipment and Kern & Sohn precision and analytical balances for bullion counters and refining operations.

Frequently Asked Questions

Final Thoughts

Tungsten-core gold is dangerous precisely because it passes the easy tests. The PMV approaches it differently by measuring resistivity through the sample and, on the Investor and PRO, adding a density test, which is a strong combination against this particular fraud. The honest caveat is Sigma’s own: it should be used together with weight, size, and provenance checks, not instead of them. With Telos Instruments, the exclusive distributor in the UAE and GCC, you can see the PMV tested against your own bars and build a verification routine you can trust.