Could be serpentine, possibly nephrite, but it could also be variscite or green turquoise if it's opaque. Those often have a tan matrix . I Can't tell from the photos if the material is semi translucent or not. If it is semi transparent, I've also seen some crysophrase in that color.
Now my first guess is serpentine. Nephrite is very tough, and though it sometimes has cracks, i think there are too many cracks in those beads for them to be nephrite. Serpentine is related to nephrite, and sometimes can look similar, but much less tough.
They look like contemporary earrings to me. Simple and easy to make. I would think stones like that are easy to find at a bead show. You might want to look around on ebay for similar.