What Metals Do Metal Detectors Detect?

Published: 3 Oct 2024

The love for metal detectors has grown increasingly over time. Some people use metal detectors as a hobby while others adopt it as a profession. These devices are used to find historical artifacts, lost treasures, or other precious metals.

But what metals can a metal detector find? This article will answer this question in detail and share all the relevant knowledge that you should know.

How Do Metal Detectors Detect Metals?

Table of Content

Common Metals Detected by Metal Detectors
Metals That Are Difficult to Detect
Factors That Affect Metal Detection
Final Thoughts

Metal detectors work on the principle of physics known as electromagnetic induction, which allows them to sense the presence of metals beneath the surface. Here is a simplified explanation of their working procedure.

The Physics Behind Metal Detection

Here is how a metal detector works:

At the heart of a metal detector is a coil of wire called the transmitter coil. When electric current flows through this coil, it generates a magnetic field around it. As you sweep the metal detector over the ground, this magnetic field moves with it.

When the magnetic field comes into contact with a metallic object, it induces small electrical currents, known as eddy currents, within the metal. These eddy currents generate their own magnetic field, which is different from the one created by the detector.

Meanwhile, the receiver coil, located near the transmitter coil, picks up the secondary magnetic field generated by the eddy currents in the metal. Once the receiver coil detects this field, the metal detector processes the signal and alerts the user through a beep, tone, or visual indicator on a display. This is the moment that every detector is waiting for.

Common Metals Detected by Metal Detectors

1. Ferrous Metals

Those metals that contain iron are called Ferrous metals. These metals are magnetic and can be detected with most metal detectors.

Iron: Irons are Often found in relics, nails, and tools. While iron is highly detectable, it is also prone to rust, which can make it tricky to identify in some conditions.

Steel: Steel is an alloy of iron and carbon. It is widely used in construction and manufacturing. Moreover, It is frequently found in objects like bolts, screws, and structural components.

2. Non-Ferrous Metals

Non-ferrous metals do not contain iron and are generally non-magnetic. However, they are still easily detected because of their electrical conductivity.

Aluminum: Aluminum is lightweight and corrosion-resistant metal. It is commonly found in modern coins, beverage cans, and foil, and it can be frequently found in parks and beaches.

Copper: Copper is Known for its high conductivity. It is often found in old coins, pipes, and electrical wiring.

Gold: Gold is a precious metal and every detector wants to find it. It is both dense and conductive which makes it detectable even in small quantities. It is often found in the form of jewelry, coins, or natural nuggets.

3. Precious Metals

Precious metals are highly valued for their rarity and economic worth. Metal detectors can easily pick up these metals, making them prime targets for hobbyists and professionals alike.

Silver: Silver is commonly found in coins, jewelry, and historical artifacts. Its high conductivity makes it one of the easier precious metals to detect.

Platinum: Platinum is also a precious metal due to its durability and rarity. It is most often found in fine jewelry and industrial applications. Its high density and conductivity make it easily detectable.

Metals That Are Difficult to Detect

1. Stainless Steel

Due to low electrical conductivity and weak magnetic properties, Stainless steel is difficult for most metal detectors to detect. While some detectors might pick up large stainless steel objects, small items, like stainless steel jewelry or cutlery, are almost impossible to detect.

2. Low Conductivity Metals

Metal detectors can hardly detect metals with low conductivity like titanium and zinc which produce weak signals that are harder to pick up.

3. Platinum

Platinum is a precious metal, and very difficult to detect on metal detectors. It also produces low electrical conductivity compared to gold and silver making it less detectable. However, some advanced metal detectors can still detect platinum, but it can be challenging, especially if the object is small or buried deep.

4. Composite Metals and Insulated Metals

The insulating material such as lead-lined objects prevents the metal detector’s magnetic field from interacting effectively with the metal, making it almost impossible to be detected.

Factors That Affect Metal Detection

Following are some of the key factors that affect metal detection:

1. Type of Metal

Different types of metals have different electrical conductivity. Metals with higher electrical conductivity, like copper and gold, produce stronger signals, making them easier to detect. Similarly, ferrous metals, with their magnetic properties, are also readily detected, though they might be confused with less desirable objects like nails or junk.

2. Size and Shape of the Object

Large-size metal objects create stronger signals. It makes them detectable even at greater depths. The shape of the object also matters; flat or elongated objects can be easily detectable whereas, metals with irregular shapes are difficult to detect. For example, a large, flat piece of metal like a coin will generate a more consistent signal than a small, misshapen fragment.

3. Depth and Ground Conditions

Apart from the size and type of an object, the degree of burial is another factor that goes a long way in detection frequency. A majority of metal detectors have rather a low detection range, from a few inches to several feet. Other factors that may influence it include highly mineralized soil, wet sand or sand, gravel, or rocky terrain among others. For example, wet ground can be beneficial in improving the conductivity of certain metals so as to make them more easily detectable, and other conditions may mute the signal.

Advanced Metal Detection

Metal detectors are not just limited to the basic ferrous and non-ferrous metals. They can also detect more complex alloys and mixed metals, each with its own unique signature.

Alloys: These are metals that are produced through the joining of two or more elements for instance bronze includes copper and tin and brass has copper and zinc. The composition of alloys is normally different and this means that they often have some unique detection signals which make it easier to identify them by more experienced personnel.

Mixed Metals and Coins: coins are one of the most interesting discoveries that are made by fans of metal detectors. Most of today’s coins are bi-metallic or tri-metallic, therefore some of the increasingly used components include copper, nickel, and zinc. Both metals help to make up the whole signal that detectors use to differentiate between numismatics of different materials.

Unusual Finds: At times the metal detectors may even detect some peculiar objects including meteorites and other metals depending on the location being scanned. Nevertheless, there are some demerits of using metal detectors; the detectors may not identify metals well in areas with high concentrations of minerals or objects that are small in size and located deep underground.

Final Thoughts

Metal detectors open up a world of possibilities, from uncovering hidden treasures to discovering historical artifacts. With this knowledge of what metals can be detected, and with an appreciation of complications such as type of metal, size, and circumstances of the ground, the possibility of success can be optimized. Whether you are an experienced aficionado or a simple newcomer to this world, metal detecting is a real chance to continue the adventure. Happy hunting!