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Short-duration light pulses have been observed to be emitted at the moment of microfracture (pit size of 10-20 µm) when two solids are rubbed against each other. When a fused silica sample is scratched by a diamond grain, the observed light pulses have a rise time of less than 10 ns and pulse width of 10-20 ns. A continuous spectrum at 500-800 nm is observed, suggesting 3000° C material part. At 300-400 nm, intense line spectra are observed, which suggests the existence of gaseous *O2 molecules desorbed from SiO2. When the solid fractures, the fractured part heats up to a very high temperature almost instantaneously, and cools down within 10-20 ns.

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