Here's a short riddle I came up with--easy, I know, but I wasn't trying very hard.

I’m often hard to break
When what I hide eludes thy grasp
But when thou hast caught it, at last
Thou’lt often give a gasp

My nature’s crystal clear,
But when thou seest me, I’m dark
Perhaps thou’lt say I’m too obscure
But carefully my words mark:

To pierce the gloom, thou’lt need
A sharp and penetrable mind
Thus thou’lt guess what another made
And what I hide, thou’lt find

P.S. Can you solve the riddle of my name?