Can my phone detect gold? What metal detector apps find

Search an app store for a gold detector and you'll find plenty of metal detector apps. Can your phone really detect gold? Not reliably, and the sensor these apps use explains why.

What the sensor in your phone measures

These apps read the magnetometer, the compass sensor. Android's developer documentation describes it as a geomagnetic field sensor: it measures the magnetic field around the phone in microtesla (µT) and lets apps monitor changes in the Earth's magnetic field. It only notices something nearby if that thing disturbs the field, and few things do so strongly: magnets and ferromagnetic metals, mainly iron, nickel and cobalt. That's why the reading jumps over a steel screw.

Why gold doesn't register

Pure gold is not magnetic. The University of Illinois physics Q&A service Ask the Van describes gold and copper as very weakly diamagnetic: a magnet pushes them away very slightly. Silver is diamagnetic too, and aluminium only weakly paramagnetic. The exception is gold or copper with magnetic impurities, which you can't count on. One Android metal detector app with more than 10 million Google Play downloads states in its own description that it cannot detect gold, silver or coins made of copper.

How a real gold detector works

A metal detector doesn't need the target to be magnetic. Its transmit coil sends out a changing magnetic field that makes electric currents, called eddy currents, flow in any conductive metal. Those currents create a weak field of their own, which a receive coil picks up. A phone's magnetometer sends nothing out; it only measures the field that's already there. Two of the designs described in a 2004 article in TÜBİTAK's Bilim ve Teknik magazine:

• VLF (Very Low Frequency), the most common type, sends a single-frequency sine wave and, according to Bilim ve Teknik, uses the phase shift of the returning signal to tell metals apart.
• PI (Pulse Induction) switches the field off suddenly and listens to the fading field from eddy currents in the target. It tells metals apart poorly but can often search deeper.

That takes dedicated hardware. Minelab's technical notes say signals from deeply buried targets can be millions of times weaker than the transmitted signal, and mineralised (magnetic) soil interferes with them, so detectors need special amplification, processing and ground balancing.

According to Minelab, most buried metal is ferrous, meaning a magnet attracts it, and is not normally sought, so coin and treasure detectors are usually set to ignore it. What a phone can sense is largely what those detectors filter out.

What a phone can find

Because steel is mostly iron, a phone held very close can react to the following, though sensors differ between models:

• Nails and screws in walls and floors.
• Steel pipes close to the surface.
• Rebar near the surface of concrete.

It won't reliably find gold, silver, copper, aluminium or plastic. Some stainless steel is non-magnetic too, so a stainless item may not register. And a quiet reading never proves nothing is there. A metal scanner that also detects non-ferrous metal can find copper pipe: the manufacturer Zircon rates its MetalliScanner MT7 for ½-inch copper pipe up to 15 cm (6 in) deep.

In Turkey, searching for treasure needs a permit

Treasure searching in Turkey falls under Law No. 2863 and the Define Arama Yönetmeliği (Treasure Search Regulation). As amended in 2020, the regulation defines treasure as a buried or hidden movable item that clearly no longer has an owner and has no scientific value, so cultural property doesn't count. In summary:

• A treasure search licence is required. The law gives the Ministry of Culture and Tourism the power to issue it; under the regulation, the museum directorate prepares it and the provincial governor signs it. None is issued for protected sites, registered sit areas or cemeteries, and it can't be transferred (Article 50).
• Only individual Turkish citizens may apply, by petition to the local civil administrator (the provincial or district governor). The area is limited to 50 m² and 10 m deep, searching under water is not allowed, a search runs for at most 15 consecutive days, and two museum specialists and other officials supervise it.
• Treasure searching without permission carries 3 months to 2 years in prison. Digging or drilling without permission to find cultural property, a separate offence, carries 2 to 5 years, reduced by a third if the place is not a sit area or other protected site (Article 74).
• Anyone who finds cultural or natural property must report it within three days to the nearest museum directorate or, in a village, to the muhtar, or elsewhere to the local civil administrator (Article 4).

This summarises the published texts and is not legal advice. We found no official source on using a detector for other purposes, such as looking for a lost ring; if unsure, ask the district or provincial governor's office first.

What our app does, and doesn't do

Metal Detector : Gold Finder reads the phone's magnetometer and has a live gauge, adjustable sensitivity and alerts. Because it relies on the same sensor, the limits above apply to it too: it reacts to iron and steel held close, not to gold. Despite the name, it does not reliably find gold, silver or other non-magnetic metals. It needs iOS 13 or later, is available only on the App Store and is not currently listed in the Turkish App Store. Full access requires a subscription, and new users get a free trial.

Drilling into a wall? See how to find pipes and wires behind a wall and whether stud finder apps work.

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