I'm currently working on a habitable super-earth and was considering using Copper Carbonate as a replacement for bone, I've heard it's both heavier and stronger although I would like to know the specifics of how strong it actually is. This would also result in a turquoise color when oxidized. However I don't know which color it would be if it was unoxidized. I specifically chose Copper Carbonate because it's relatively easy to evolve on my copper-rich superearth. Feel free to suggest other compositions too. Thanks in advance!
Basic copper (II) carbonate reacts with water or the moisture in the air, and forms copper (II) carbonate hydroxide, or malachite. Malachite is softer than hydroxyapatite (the main component of bone), and has perfect cleavage in one direction and fair in another, compared to the poor cleavage of hydroxyapatite. This becomes important because it means that malachite will be easier to fracture along certain planes, making it structurally weaker.
Overall, it also means copper carbonate isn't very useful as a bone material in comparison, and certainly not stronger.