Explainer
What can a metal detector detect?
Any metal can set it off, aluminum included: iron, steel, copper, brass, silver and gold. What differs is how clearly it reads them. Most detectors show a target ID to help, such as the Manticore's 2D IDs from 0 to 99 with ferrous indication.
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Every metal, some more clearly than others
A detector sends a field into the ground through its coil. A metal object in that field disturbs it, and the detector turns the change into a tone. Any metal does this, so iron nails, aluminum cans, copper coins, silver rings and gold all register.
The strength of the reply depends on the object's size, shape and metal, and on its distance from the coil. A large flat coin replies clearly. A thin flake or a small nugget replies faintly, sometimes too faintly to hear.
How to sweep the coil
- Sweep side to side
- Close to the ground
- Target in the field
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How a detector tells targets apart
Most detectors put a number on each target. The scale is the maker's own, so a number on one model does not carry over to another. For the X-Terra Intrepid, Minelab lists 0 to 98 (ferrous 0-30), so iron reads at the low end. The Manticore adds a second axis, with a ferrous indication on its 0-99 scale.
Discrimination uses that number to stay silent on some targets. The X-Terra Intrepid has Non-Ferrous and All Metal modes: the first ignores iron, the second sounds on everything. An ID is a reading of the signal, not a label on the object. Different metals can land on the same number, so dig what you are unsure of.
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Small targets and gold
Small, thin or low-conductivity targets are the hard ones: fine jewelry, foil and small gold. Makers answer with higher frequencies or with pulse induction. The Gold Monster 1000 runs 45 kHz, against 6.5 kHz on Garrett's ACE 200.
Our page Can a metal detector detect gold? compares five gold models, and our depth guide explains why we quote no depth.
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What a metal detector does not find
Glass, plastic, wood, bone and gems give no signal of their own. Some mineralized rocks and soils do, which is why gold models offer ground settings. A diamond in a gold ring is found through the ring. A detector also tells you nothing about what lies beside the metal, such as a pot or a grave. That is where the law comes in.
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Old objects and the law
On federal public lands and Indian lands, an item falls under ARPA only if it is at least 100 years old. Its regulation does not count coins and bullets as archaeological resources unless they are found with such resources, as the table below sets out. That exclusion is not a permission to dig: other rules still apply where you hunt.
| Land | Rule | Text |
|---|---|---|
| Federal public lands and Indian lands Digging or removal prohibited | Excavating, removing, damaging or defacing an archaeological resource, or trying to, is prohibited without a permit or a listed exemption. A knowing violation is a federal crime. | 16 U.S.C. 470ee(a) and (d) (opens in a new tab)Read Oct. 16, 2026 on law.cornell.edu |
| Federal public lands and Indian lands Definition | An item is an archaeological resource under ARPA only if it is at least 100 years old. | 16 U.S.C. 470bb(1); 43 CFR 7.3(a) (opens in a new tab)Read Oct. 16, 2026 on law.cornell.edu |
| Federal public lands and Indian lands Definition | Coins, bullets and unworked minerals and rocks are not archaeological resources unless found in a direct physical relationship with archaeological resources. | 43 CFR 7.3(a)(4)(ii) (opens in a new tab)Read Oct. 16, 2026 on ecfr.gov |
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Questions
Yes. Aluminum is a metal, so cans, foil and pull tabs all sound. A discrimination mode can quiet some of them, but an ID number is not a sure way to tell aluminum from a ring.
Yes, as it finds any metal. Small nuggets are the hard part, so gold models use higher frequencies or pulse induction, as section 3 shows.
Not on their own: a gemstone gives no signal. A stone set in a metal ring or pendant is found through its metal.
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