This citrine and agate ring is from Barney's Co-Op. It's positively lovely.
These next two are my favorites and are part of a collaboration between Urban Outfitters and Dara Ettinger, a LA based jewelry designer. I think the gold stone is my favorite!
Finally from Free People a GORGEOUS ring with a dazzling green stone. This would be perfect with a breezy t-shirt, a pair of comfy boyfriend jeans and a pair of Keds at brunch. I can taste the bellinis now!