It’s a painting of Venus, seated nude in front of a mirror. She is wearing pearl drop earrings, one black and one white (one can be seen in the mirror). The painting is at the Metropolitan Museum of Art in NYC, and their museum gift catalog used to carry earrings based on her earrings in the painting.
I’d like to know the name of it and the name of the artist. If anyone has old Met gift catalogs, it’ll probably be in there. 
Your description rang a bell, but I didn’t find exactly what you described. There is one Titian painting that matches your description quite closely ([URL=http://www.mystudios.com/art/italian/titian/titian-venus.html]here) but Venus wears two white earrings, and the painting is in Washington National Gallery of Art.
The Metropolitan Museum does have a Titian Venus, but no mirrors or earrings in sight. FWIW, searching throught their collection for Venus paintings didn’t provide positive results.
Do you remember the style or period of the painting?
The web site for the Met store says the earrings are from Venus in Front of a Mirror,a famous painting by Peter Paul Rubens (Flemish, 1577–1640).
It’s the Rubens, yes! Thanks. 
Well done, ratatoskK. I checked the museum store but hadn’t realised that I could click on the picture of the pearl earrings: I thought that was the only one they had. It sure looks like what the OP asked about.
BTW, that specific picture mentioned in the Museum store description is not present in the on-line catalogue of the museum. Doesn’t have to mean that it isn’t there, maybe the catalogue is not complete. I don’t have a Rubens catalogue to look it up.
I googled a bit and only found a reference to a Venus and Cupid by Rubens that is in the Museo Thyssen-Bornemisza, and is actually based on the Titian painting. The link has a picture, dunno whether that’s the one the OP meant.
I googled and it looks like he did a couple of them. This looks like it may be the one.
http://www.mezzo-mondo.com/arts/mm/rubens/RUP006.html