This looks like petrified wood to me.

[BigDan]

The thing that I think is so neat, is that the color is still there! I don't know that the pictures do it justice. What do you guys think, pertified wood? I picked it up on the Mackinaw River in Illinois.

Big Dan

 

[marinedad]

looks like it could be iron stained quartz, i have some from north carolina that looks similar. just a guess.