Or more accurately, a short story from a book. It's science fiction, possibly fairly old ('60s onward), and I remember reading "Soldier from Tomorrow" (http://en.wikipedia.org/wiki/Soldier_(The_Outer_Limits)) in a related book, might have been Outer Limits or something similar.
I'm vague on the story but along these lines: two characters from two different races find themselves on a rather large patch of sand. They are separated by an invisible wall, which only permits non-organic material (e.g. rocks) to pass it. The two must fight for survival, against each other. It could have been that their civilisations were at stake, maybe.
![](/static/smilies/thumb.gif)
I'm vague on the story but along these lines: two characters from two different races find themselves on a rather large patch of sand. They are separated by an invisible wall, which only permits non-organic material (e.g. rocks) to pass it. The two must fight for survival, against each other. It could have been that their civilisations were at stake, maybe.
![](/static/smilies/thumb.gif)