Slag
Slag is the glassy, often bubbly waste left behind when metal is made from ore, and it is the most common rock mistaken for a meteorite.
When people make iron and other metals, they heat rocks called ores in furnaces. The metal is collected, and the leftover melted rock is thrown away. It cools into a hard, dark material called slag. For hundreds of years slag has been dumped near old ironworks, spread on paths and used under railway tracks, so it turns up in many places.
Slag fools people because it can be heavy, dark and even magnetic, since it often contains bits of iron. But there are good clues. Slag is often full of round holes made by gas bubbles, called vesicles, while meteorites almost never have them. Broken slag can look shiny and glassy, sometimes with swirls of colour. Real meteorites, such as a stone from the Chelyabinsk fall in Russia in 2013, have a thin, dull fusion crust and a grey, grainy inside.
If you find something you think is a meteorite near a railway line, old factory or farm track, slag is the most likely answer. Slag can have sharp, glassy edges, so handle it carefully, and never collect on railways or private land without permission.
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Level: Beginner Ages 7 and up