Fulgurites, formed when lightning hits sand or silica with a temperature of at least 1,800 °C (3,270 °F), started being formed in these places. The heat melts sand on a conductive surface and fuses mineral grains together; the fulgurite tube is the cooled product. This process occurs over a timespan of around one second, and leaves evidence of the lightning path and its dispersion over the surface or into the earth. Singapore is one of the world's lightning capitals, getting hit by 186 days of lightning a year.