I don't mean to imply that one needs to carry a Rambo sized knife in the woods. I carry a blade between 3 1/2 and 4 1/2 inches. My daypack has a Mora 510 in it and I have used that for awhile now.

A blade made from a rock may be useful for some knife work but to use it for long will be mighty uncomfortable on the hand. My Mora 510 and sheath weighs less than 3 ounces, less than a Spydeco Tenacious.