iron sand pavement

Was that the sound of her anklebones shattering? No, it wasn’t.
The sound of the giant arm made of countless pieces of scrap coming down to strike her?
No, not that, either.
It was the sound of somebody severing the arm.
(Wha...Eh...?)
She opened her eyes, surprised at the sudden strike.
The arm had been cleanly cut in two at the wrist. Before she could give it a closer look, the
“teeth” holding her ankle in place were mowed down. Suddenly freed from her shackles,
she toppled over backward. As soon as the hand was severed, all the materials composing
it reverted to their normal state and flew off in all directions.
A strange sound hundreds of times louder than the buzzing of bees assaulted her ears.
When she looked, she saw something floating in the air. It was like a black whip or like a
rapier many meters long. That’s where the sound was coming from. Closer inspection
revealed that it was iron sand. An enormous clump of iron was being controlled by
someone, possibly with magnetism, and it was vibrating.
In other words, it was a supersonic chainsaw.
A piercing sound rang out as the iron whip returned to its owner.

- Toaru Majutsu no Index Volume 6, Between the Lines 1