Australian Science Teacher Jacob Strickling demonstrates the surprising result when a fabric gas mantle is brought towards a Geiger counter.
Mr Strickling first demonstrates the radioactivity the Americium-241 from a smoke detector is. The Americium-241 is such a small sample it needs to be lodged in the red plastic disk.
He then brings the fabric gas mantle used in gas camping lanterns towards the Geiger counter. The Geiger counter again starts rapidly clicking away showing how radioactive the gas mantle is. The mantle contains Thorium Dioxide (a radioactive compound) which causes the mantle to glow a bright white when heated. Fortunately the radioactivity emitted is stopped by a short distance in air, so the mantle is quite safe (unless you chose to eat it of course)