1.   His eyes hardened to slivers of jet as he spoke.

2.   His night-dark eyes hardened to cold jet.

3.   His eyes harden, his hands strain toward fists.

4.   When he talks about the Taliban, though, his usually twinkling eyes harden.

5.   But a brief smile vanished and his eyes hardened when asked when he thought he would be returning, dismissing talk of a cease-fire.

6.   When a policeman tussled his hair, he drew back sharply, eyes hardening with hatred.