There's an interesting book called "Fiber Menace".

He points out that poops are formed mostly from bacteria, and that "fiber" is not necessary to make them. (Notice a baby drinking only milk, not a bit of fiber, and they poop just fine, sometimes several times a day.)

So, if you are passing hard little rocks once or twice a week, "dysbiosis", the lack of intestinal flora, may be the cause. They are hard because the longer they stay in the colon the dryer they get. Bacteria in poops hold in the fluid, so they are soft.

He thinks that healthy poops are small, soft, and numerous. "Fiber" filled poops are big, may have been around for a long time, and do a lot of damage because you have to strain to drive them out.

If you're interested in his approach, here's more than you ever wanted to read about poop: