Design Alien Skeleton w/ Copper, Calcium & Element: Tip?

[Yemmy]

Could calcium and copper and say - boron, be joined into one substance?
If not boron, then which element?
I am trying to design an alien skeleton with copper, calcium, and ?
I love copper and part of the idea is its distribution throughout the universe.
I am asking for a tip about where to look for this info, unless someone out there has element mixing knowledge resting on the tip of their brain.
Thank you.

 

[mfb]

You can mix basically all metals together, and smaller amounts of nonmetals inside are possible as well. Not everything will lead to properties you want for bones (chemically passive, reasonable melting point, high structural strength, not too heavy, ...), and not everything will be useful for life (available in the environment, suitable chemical pathways to produce it, ...) but in a fictional setting there is more freedom in the parameters.