Hi...thought I'd posted this last night, but can't find it today. So please excuse it, if it's a duplicate.

My bathroom copper sink (round with dragonflies...don't know the maker, as it was installed by a preious owner) seems to be developing an unexpected patina...or something.

When I first moved in the sink looked awful...gunky looking black "drip" lines and splotches. I read up on this site and others about patina, developing and protecting them and decided that my best bet was to start fresh. So, I scrubbed the sucker till it was ALL shiny, using softscrub (as someone here suggested) and the old salt and vinegar routine for tough spots.

Then I sat back and waited for it to darken again, figuring when it reached an appropriate place, I'd wax it. That seems to be happening pretty nicely in most of the sink. But around the drain, it's taking on a silvery, slightly greenish cast. It started as just a 1/2 inch wide ring and is spreading out and now turning the pop-up drain as well.

I suppose it is POSSIBLE that it's developing a sort of verdigris patina, but it looks more silvery/steel than green. I'm wondering if it is possible that this sink is not solid copper, but actually steel or aluminum coated with copper? Is that possible/likely?

If it is a greenish patina...well, it's unexpected, but OK with me. I just hope I haven't ruined the darned thing altogether.

Any thoughts?