What is a meteorwrong?
A meteorwrong is a rock or object that looks like a meteorite but isn't. Common examples include industrial slag, iron ores such as magnetite and hematite, dark volcanic rock, flint and rusty bits of manufactured iron.
The word is a playful twist on "meteorite", and every meteorite specialist sees far more meteorwrongs than real meteorites. Museums that offer identification find that the overwhelming majority of rocks sent in turn out to be earthly. That is not a failure: learning to spot meteorwrongs is part of learning what genuine meteorites look like.
The most common culprit is slag, the glassy waste left over from smelting metal. It is often dark, heavy and magnetic, which fools people, but it is usually full of gas bubbles and can have a glassy or swirled look. Next come the iron ores magnetite and hematite. Both are dense and dark; magnetite is strongly magnetic, and hematite leaves a reddish-brown line when scraped on an unglazed tile.
Dark volcanic rocks such as basalt are another favourite, especially when weathered smooth, but they often have holes from gas bubbles and lack metal. In Britain, black-skinned flint nodules from chalk are frequently mistaken for meteorites; a chipped flint shows glassy, shell-shaped fractures. Rounded iron-rich concretions, which grow inside sedimentary rocks, can look like cannonballs from space. And scraps of manufactured iron, from old tools to machine parts, can rust into convincing shapes.
The key is to look for several meteorite features together: a thin fusion crust, no bubbles, metal flecks inside, weight and magnetism. One clue alone proves nothing. If you are unsure, ask a museum or university geology department, and resist the urge to cut, heat or put acid on a specimen to find out. Those tests can be dangerous and can ruin a real meteorite.