Can a Metal Detector Detect Copper and Brass?

Can metal detectors detect copper? Yes. Copper is detected extremely well, and brass reliably. Copper is the reference metal for electrical conductivity and produces one of the strongest, highest-reading signals of any common metal. Brass, an alloy of copper and zinc, is less conductive, so it typically reads in the middle of the target ID range rather than at the top. Both are common finds, from old coins and buttons to wire, fittings and shell casings.

This guide covers how metal detectors detect copper and brass, how they read compared with silver and gold, and what you are likely to find.

Can metal detectors detect copper? Why the signal is so strong

Metal detectors that use electromagnetic induction transmit a field from the search coil. Conductive metal in that field carries induced eddy currents, and those currents create a field the detector receives. The more conductive the metal, the stronger and more phase-shifted the response tends to be for an object of a given size.

Copper is the benchmark for this. The International Annealed Copper Standard (IACS) defines annealed copper as 100 percent conductivity. Only silver is more conductive among common metals. That puts copper targets at or near the top of most detectors' target ID scales, alongside silver.

Copper is also non-magnetic, so detectors classify it as a non-ferrous target.

How brass compares

Brass is copper alloyed with zinc, typically somewhere between about 5 and 40 percent zinc. Adding zinc lowers conductivity substantially. Based on standard handbook resistivity values, a common 70/30 brass (such as cartridge brass) has roughly 28 percent of copper's conductivity, while low-zinc brasses conduct much better. Bronze, which is copper alloyed mainly with tin, generally falls lower still.

Conductivity values are rounded from standard resistivity data at room temperature. ID positions are general tendencies; size and shape often matter as much as metal type.

Remember that target ID depends on size as well as conductivity. A large brass object, such as a heavy plumbing fitting or a big buckle, can read higher than a small copper item because there is more metal for eddy currents to flow through. See our guide to reading target IDs for more on how this works.

Copper and brass finds you can expect

Coins

US coins are a big part of copper finds:

• Large cents and early small cents, plus Indian Head cents and most Lincoln cents dated before 1982, are mostly copper and read high.
• Lincoln cents from 1982 onward are copper-plated zinc. Because zinc is less conductive, these modern cents usually read lower than older copper cents.
• Nickels are 75 percent copper and 25 percent nickel, but the alloy reads much lower than pure copper, often in the low-to-mid range.
• Clad dimes and quarters have a pure copper core between copper-nickel faces and generally read high, near silver.

The US Mint publishes coin compositions, and dates matter a lot for detectorists. If you want to know which ones are worth more than face value, see valuable coins found metal detecting.

Relics

• Brass and copper buttons, buckles, tokens and badges.
• Harness and tack hardware.
• Brass cartridge cases and some percussion caps.
• Copper and brass household items: thimbles, keys, lamp parts, spoons.

Modern trash

• Copper wire offcuts, electrical connectors and plumbing fittings.
• Brass screws, keys and zipper pulls.
• Bottle caps and other mixed-metal items.

Can a detector tell copper from silver?

Usually not with certainty. Copper and silver are so close in conductivity that their IDs overlap on most machines. Some detectorists learn to notice subtle differences on their own detector, but a high-conductor signal should be treated as "worth digging" rather than labeled in advance. The same applies to telling brass from gold: both can fall in the middle range.

Detecting native copper

Native copper occurs naturally in a few places, most famously in the Keweenaw Peninsula area of Michigan's Upper Peninsula, where copper float and nuggets are found in glacial deposits and old mine waste rock. Because native copper is nearly pure, it responds strongly to metal detectors, and detecting for copper and "silver-copper halfbreeds" is a recognized pastime in that region.

If you plan to search for native copper, check land ownership and rules carefully. Mine rock piles and lands in that region may be private property, state land or tribal land, each with its own rules on access and collecting. Always obtain permission where it is required.

Best settings for copper and brass

1. For old copper coins, a lower-frequency or multi-frequency mode usually performs well on high-conductors. Ground balance properly and use moderate discrimination.
2. For brass relics, keep the mid-range open. Brass buttons and buckles often read where pull tabs and screw caps do.
3. Corrosion matters. Copper and brass develop green or brown corrosion that can weaken or distort the signal slightly over time, especially in wet or acidic soil.
4. Watch out for iron masking. On old home sites, iron nails can hide nearby copper coins. A slower swing and a smaller coil help.

Our guide on cleaning coins found metal detecting explains when to leave a copper coin's patina alone. Aggressive cleaning can destroy value.

Copper and brass in wet or mineralized ground

Ground conditions change how copper and brass targets sound. In highly mineralized soil, the ground itself produces a signal that competes with the target, which can push target IDs around and reduce depth, especially on VLF detectors. Salt water and wet, alkaline soil can have a similar effect. Long-buried copper coins may also develop a corrosion "halo" in the surrounding soil, and some detectorists report that this makes old coins easier to hear, though the effect varies and is hard to measure.

Practical steps help in difficult ground: ground balance carefully and re-check it as conditions change, reduce sensitivity slightly if the detector becomes unstable, and confirm signals from more than one direction before digging. If the ID jumps but the audio is solid and repeatable, it is often still worth recovering.

Copper wire and buried cable

A metal detector can respond to buried copper wire or cable, especially near the surface, but a hobby detector is not a utility locator. Long, thin conductors produce signals that are easy to misread, and depths of buried utilities vary. Never rely on a metal detector to clear a dig site. In the US, contact 811 before digging so utilities can mark their lines. Our article on finding underground pipes and cables covers this in detail.

Choosing a detector for copper coins and relics

For coin and relic hunting, look for:

• A clear, stable target ID with good separation between iron and non-ferrous targets.
• Low or multi-frequency operation for high-conductivity targets.
• Good recovery speed for trashy sites.
• Coil options for depth versus separation.

Browse general-purpose and relic-capable detectors in our metal detectors collection.

Frequently asked questions

Does copper set off a metal detector?

Yes. Copper is one of the most conductive metals and produces a strong, high-reading signal on induction metal detectors.

Can a metal detector detect brass?

Yes. Brass conducts less well than pure copper, so it usually reads in the middle of the target ID range, but it is reliably detected. Large brass objects can read higher than small ones.

Why do new pennies read lower than old pennies?

Lincoln cents from 1982 onward have a zinc core with thin copper plating. Zinc is much less conductive than copper, so modern cents generally read lower than older, mostly copper cents.

Can I tell a copper coin from a silver coin before digging?

Not reliably. Their target IDs overlap on most detectors. Dig high-conductor signals and check what you have.

Can a metal detector find copper ore?

Native copper nuggets respond well. Most copper ore minerals, however, are compounds dispersed through rock and do not produce distinct detector signals. Ore exploration relies on geology, sampling and assays.