1.   He had been picking up rock fragments that had apparently been chipped by human ancestors.

2.   Primitive bacteria could have hitched a ride on rock fragments crossing interplanetary space and seeded life on Earth, he says.

3.   Rock fragments bounce off helmets.

4.   Pyroclastic flows are the result of explosive eruptions of molten or solid rock fragments, or both.

5.   Authorities expanded the danger zone in part because the volcano possibly could shoot hot rock fragments into Salem, causing building fires, Sergeant said.

6.   Emergency officials feared some villagers may have been trapped by clouds of superheated gas, ash, and rock fragments that sped down the slopes of the Mayon volcano.