I do not know about you all, but all my tattoos have meaning and were well thought of. I share ( along with many other Satanist ) the same brimstone tattoo.
Justin and I brimstone tattoos.

Dave Navarro brimstone



Still, always nice to see someone repping.
It would surprise me if it's an alchemy thing for him, since it, apparently referred to as the "pontifical cross of Satan" by some non-Satanists, more than likely is viewed like the swastika (i.e. according to its most recent application).
Here's another funny example.

A newer Christian symbol. Haha!
So, it appears either Navarro is either into alchemy or has come out as a Satanist.