Can a metal detector find stony meteorites?
Often yes, because most stony meteorites contain iron-nickel metal grains, but signals are weak and depend on the detector, the stone and the ground.
Metal detectors are best known for finding iron meteorites, but they can also detect many stony meteorites.
Why it works. Most ordinary chondrites contain iron-nickel metal, from a few per cent in LL chondrites to about 15 to 20 per cent in H chondrites. This metal is spread through the stone as small grains, which together produce a detectable signal.
Limitations. The signal from a stony meteorite is weaker than from a solid iron of the same size. Small stones, or those deep in the ground, may be missed. Heavily weathered stones, where metal has turned to rust, give weaker signals. Some meteorite types contain very little metal, such as many carbonaceous chondrites and achondrites, and may not be detected at all.
Ground effects. Mineralised soils, especially those rich in iron oxides, can cause false signals. Detectors designed for gold prospecting often handle such ground well.
Technique. Hunters sweep slowly and systematically. Many signals will be from iron rubbish such as nails, wire and farm machinery parts, so patience is essential. Testing the detector on a known meteorite of similar size helps calibrate expectations.
Rules. In many countries, metal detecting is regulated. In the UK, you need the landowner's permission, and detecting on scheduled ancient monuments is illegal without consent. Archaeological finds may need to be reported. Check the current rules for your location.
In practice, many stony meteorite finds are made by eye, with detectors used to check candidates or search for buried irons.