little sterling earring with black stone

This is a small silver earring for pierced ears, sort of a 'cross' design in relief with an even smaller round black stone set in the center. Shown with a US 25c coin for size reference in the first couple pics, it ain't very big. Pic 4 is me wearing it in my newest actual piercing (a 2nd on that side was long overdue, the other ornament there is a 12ga. surgical stainless 'circular barbell') along with the sterling necklace chains I've recently...uhh..."invested in"...? <lol> (their stories already shown here recently, too) Barely visible in pic 3 it is marked "925" and "SU" on its backside -- I tried my best but it's difficult to see even in real life. I have no idea what the little black stone in it might be.

I also really don't remember where/when I got it -- I've only got the one and I've had it for decades, likely never even really wearing it (it was tarnished quite black when I recently came across it again) thus it's just as likely to have been picked up off a floor or any one of countless other random places...who knows. But when I got this recent ear piercing, the initial stud jewelry proved a little irritating at first (I sleep on that side?!) so I went looking around for another, finding this -- it polished up quite nicely and is *much* more comfortable to wear -- frankly I've grown fond of it though my intent was just to get a tastefully small diamond/CZ stud in a silver setting...I might just keep wearing this one instead?! ;-) :-) :-)