Arsonists often leave matches behind, assuming they will burn away to nothing. But the powdered rock in a match head contains the fossilised remains of single-cell algae called ‘diatoms’. A diatom’s shell is made of silica, which is abrasive enough to help you strike the match, and tough enough to endure extremely high temperatures. Each of the 8,000 known species of diatom has a unique shell structure, identifiable through a microscope. Different brands make their matches using powdered rock from different quarries. If forensic scientists can spot the diatoms, they can identify the match
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