Trying to find an old science fiction book I never finished reading as a kid. It was mid 90's when I picked it up, it was from my dad's old book collection so I don't know exactly how much older it was.
I remember the book was kinda old, as it had an American travel to another planet to prevent the communists from corrupting the primitive inhabitants which were pretty human. The key detail I can remember is the man made a very durable knife out of some sort of crystal to prevent the inhabitants of learning about his technology.
I never got far into the book and I seem to remember the cover having a guy fighting an animal with a knife in a jungle setting, but I could be mixing the cover memory up with a different book cover.