I have a post-apocalyptic world where some intelligent animals become the new major world-controlling species. In particular, some new/evolved species of Cuttlefish and Octopi are beginning to fill the world-dominating niche we humans currently enjoy. We know (real-world) cephalopods are really smart, and can even open jars while stuck on the inside: this story is just assuming those creatures gain more intelligence and humans are more-or-less removed from the picture.
These cephalopods can't do everything on their own, though, and becoming the dominant species/society requires some tool use. I just can't seem to justify getting my super-smart cephalopods out of the stone age. Iron rusts and corrodes in the ocean. Bronze requires alloying, which generally requires fires. Also, the ocean has a tendency to corrode/dissolve metals.
How will I get my octopi/cuttlefish beyond stone-age technology? More specifically, what metals can these cephalopods develop and use in the ocean?
You may assume:
- real-world values for everything except for the cephalopod intelligence
- these smart cephalopods are about as intelligent as humans.
- You can safely assume an octopus can use their tentacles for the same purposes we use our hands.
- Plastics, from humans, are still around but not being made. Computers, electric grids, and other remnants of human civilization are out-of-reach (and sight) or decayed beyond usefulness.