Is that a meteorite?

Few items in modest local museums are misattributed as often as alleged meteorites. If there were bogus Picassos about on the same scale, the curators would be fired en masse.

Meteorites and tektites sold by dealers are usually the real deal. (The same cannot be said of the wares peddled by some of the more imaginative fossil dealers.)

Meteorites come in two kinds. One are the falls, meteorites actually seen falling from the sky. The odds on your seeing such a sight are incalculably long, but it does happen a few times a year. If it does, the provenance of the rock in question – as the antique dealers might say – is pretty solid.

The other group are the finds.These are meteorites that are, well, found, either by chance or by searchers looking for them after reports of a fall. A fresh one might well have a fusion crust, a black outer layer from the heat of its passage through the atmosphere. An iron meteorite might well look shiny, and will be unexpectedly heavy for its size. But a stony one, although it will be darker than most Earth rocks, is more likely to be missed. This is why there are fewer stony meteorites among finds than among falls. The most distinctive are the chondrites because of the little spotty bits – the chondrules – that they contain.

Another clue is that meteorites tend to flock together in “strewn fields”. So if you have found one, you might find another nearby.

Most of the bogus meteorites, incidentally, are in museums in areas where iron smelting has been a local industry. They are discarded bits of furnace slag. Top tip – if you do find a freshly fallen meteorite, bag it up in something airtight. The gases it contains are full of scientific information but are lost after a spell in the open air.