How to Verify Gold and Silver Bullion: A Safe Testing Decision Tree
To verify gold and silver bullion safely, start with the seller and product record, then compare design, weight and dimensions with official specifications. If uncertainty remains, add the right non-destructive test for the product—resistivity, density, XRF or ultrasound—and treat every result as one layer of evidence rather than automatic proof.
- No single home test proves that bullion is genuine.
- A magnet is useful for rejecting some obvious fakes, not confirming gold or silver.
- Correct weight without correct dimensions is incomplete evidence.
- Assay packaging and serial numbers support identification but can be copied or altered.
- Electronic resistivity and density tests are strongest when matched to the correct alloy and product dimensions.
- XRF is highly useful for surface composition; it does not automatically prove the interior.
- When value or uncertainty is high, stop and use a qualified dealer, refiner, assayer or recognized grading service.
The bullion verification decision tree
Can you document where it came from?
Keep the invoice, seller identity, listing, shipment record, assay card and photographs. If provenance is weak or the seller is pressuring you, increase the level of testing before money changes hands.
If no: do not rely on appearanceDoes the product match an official reference?
Compare the exact design, inscriptions, edge, mintmark, dimensions, weight and fineness with the mint, refiner or grading-service reference for that product—not with a similar marketplace photo.
If no: stop and escalateDo precise weight and dimensions agree?
Use a calibrated scale and calipers. A correct weight paired with wrong thickness or diameter is a warning. Allow only documented manufacturing tolerances and normal wear.
If no: quarantine the itemIs basic screening consistent?
Check magnet response, surface quality and packaging without scratching or opening a sealed product unnecessarily. Passing these checks does not authenticate the item.
If uncertain: add instrument testingWhich instrument answers the remaining question?
Use resistivity/conductivity for alloy consistency, density for bulk physical consistency, XRF for surface elemental composition, or ultrasound for internal interfaces in suitable bars. Use more than one method when the risk warrants it.
Match method to productDoes every result agree?
A pass means the sample is consistent with the selected test and reference. It does not prove provenance, mint origin, collector grade or an untouched interior beyond the method’s reach.
If conflict remains: professional reviewStart with the seller, not the gadget
The safest authentication program begins before the product arrives. Buy from a dealer who clearly identifies the item, provides return and inspection terms, documents shipping and stands behind authenticity. A testing device cannot repair a bad transaction with an anonymous seller who disappears.
For carded bars, record the refiner, weight, fineness, serial number, card design and visible security features. An assay card is useful packaging and identification evidence, but it is not an independent guarantee that the bar was never switched. Read Agate’s focused guide to assay cards, serial numbers and sealed packaging.
What each test can—and cannot—tell you
| Method | Useful for | Main limitation | Best role |
|---|---|---|---|
| Visual reference | Wrong fonts, design details, edge, packaging or dimensions | High-quality fakes can look convincing | First-line comparison |
| Weight and calipers | Finding wrong mass, diameter or thickness | Density substitutions can be engineered to mimic one measurement | Required physical screen |
| Magnet | Rejecting strongly magnetic base metals | Gold, silver and several counterfeit materials are nonmagnetic | Fast rejection test only |
| Specific gravity/density | Checking whether bulk density matches the expected alloy | Needs accurate weight/volume and can be awkward for packaged items | Strong second layer |
| Resistivity verifier | Comparing electrical response with a selected precious-metal alloy | Correct alloy selection, sensor placement, thickness and device range matter | Non-destructive coin/bar testing |
| XRF | Identifying surface elemental composition and fineness | Primarily a surface/near-surface technique; plating can require another method | Alloy and surface screening |
| Ultrasound | Finding internal discontinuities or inserts in suitable larger bars | Shape, thickness, coupling and operator interpretation matter | Interior examination of appropriate bars |
| Acid or scratch testing | Traditional alloy screening on exposed material | Can damage surfaces and samples only the tested area | Not for collectible coins or intact assay cards |
Magnet test limitations
Gold and silver are not ferromagnetic, so a strong attraction is a clear problem for a product expected to be solid gold or silver. The mistake is treating “not attracted” as “genuine.” Copper, lead, tungsten and many other materials also are not strongly magnetic.
Some users perform a magnet-slide test because conductive metals can slow a moving magnet through eddy-current effects. Shape, orientation, surface, magnet strength and alloy influence the result. It is useful only as comparison evidence against a known genuine product. Do not drop or scratch a collectible coin to hear a ring.
Weight, dimensions and density
A counterfeit maker can hit the expected weight by changing thickness or diameter. That is why these measurements belong together. Compare with the specification for the exact product and use equipment precise enough for the size involved.
Density adds another check because gold and silver have characteristic densities. Yet a density result still depends on accurate measurements and a clean method. Hollow pieces, trapped air, jewelry components and packaging can distort a home calculation. Sigma Metalytics states that certain PMV models combine resistivity with density-related measurements; follow the manual for the exact model.
Sigma Metalytics and resistivity testing
A Precious Metal Verifier measures how a sample responds electrically and compares the reading with the expected range for the selected alloy. Sigma says the signal can reach below the surface and some models can test through nonmetallic holders or assay packaging.
The result means the tested sample is consistent or inconsistent with the selected alloy under the instrument’s conditions. It does not identify a rare variety, guarantee a numerical grade, prove a serial number belongs to that bar or replace weight and dimension checks. Sensor size and penetration capability vary by model and accessory. Agate’s separate Sigma Metalytics testing guide covers those limits without duplicating the full workflow here.
XRF and ultrasound
X-ray fluorescence identifies elements by measuring characteristic X-rays emitted from the tested area. It is fast and non-destructive, making it valuable for checking surface composition and stated fineness. Because it reads the surface and a limited near-surface depth, it should not be treated as a universal test for the center of a thick bar.
Ultrasound can help detect internal interfaces or unexpected sound velocity in suitable larger bars. It requires correct calibration, good contact and an operator who understands the expected geometry. For high-value bars, combining surface chemistry, bulk measurements and an interior-sensitive method is stronger than repeating the same type of surface test.
Choose the correct branch for the product
Sovereign bullion coin
Compare official diameter, weight, thickness, edge and security features. Add resistivity or density when needed. If the coin may also have collector value, use a recognized coin authentication/grading service rather than destructive testing.
Generic silver round
Confirm weight, diameter, thickness and design. Magnetic screening and a verifier can help, but obscure designs may lack a strong visual reference. See Agate’s guide on testing whether a silver round is real.
Carded gold bar
Document the entire card and serial number. Compare the card seams, print, dimensions and refiner reference. Use a method rated to test through the nonmetallic packaging when possible; do not open the card unless the transaction terms and testing plan justify it.
Large silver or gold bar
Weight and dimensions are essential, but thicker material may require more than a surface test. Depending on the bar and value, a professional may combine XRF, ultrasound, conductivity and density.
Continue into the specialized Agate guides
Frequently asked questions
Can a magnet prove that gold or silver is real?
No. Strong attraction can reject an expected gold or silver item, but many counterfeit materials are also nonmagnetic.
Can Sigma Metalytics test through an assay card?
Sigma states that its devices can test through many nonmetallic cases, holders and assay packages. The correct sensor, alloy setting, thickness range and placement still matter.
Does XRF test all the way through a bullion bar?
No. XRF is primarily a surface and near-surface elemental analysis method. A thick bar may need bulk or interior-sensitive tests as well.
Should I open a sealed gold bar to test it?
Not automatically. First use product references and appropriate non-destructive testing through the package. Opening the card can affect presentation and resale.
What should I do if two tests disagree?
Stop the transaction or quarantine the item. Recheck the exact reference and instrument settings, then seek qualified professional testing rather than forcing a conclusion.
Sources
- Sigma Metalytics: PMV Original and resistivity-testing overview
- Sigma Metalytics: device and testing FAQs
- CFTC: Avoid Problems When Buying Precious Metals
- NGC: Counterfeit Detection resources
Disclosure: No screening method guarantees authenticity in every situation. Instrument capabilities vary by model, sample, calibration and operator. This educational guide is not a certification, appraisal or purchase guarantee.