Source : Webster's Revised Unabridged Dictionary (1913)

Pele's hair \Pe"le's hair\ [After a Hawaiian goddess associated
   with the crater Kilauea.]
   Glass threads or fibers formed by the wind from bits blown
   from frothy lava or from the tips of lava jets or from bits
   of liquid lava thrown into the air. It often collects in
   thick masses resembling tow.