I'm working in the American Embassy in Mauritania right now. I have seen (and bought) beads very similar in appearance to these green stone beads--similar shapes, same range of green colors and degree of translucency--in both Mali and Mauritania. Jamey mentions China as a possible origin for beads like these. I can't rule that out, but specifically for the beads I bought in Mali and Mauritania, other origins seem more probable, given that until very recently there were not many Chinese beads circulating in Africa (a very few found in Great Zimbabwe ruins are the only ones I know of until the late 20th c.). For the ones I bought, perforation wear and general appearance of the beads I bought would tend to indicate a few score years of wear--although the stone is relatively soft so they may not be as old as they appear.

Change of subject:
There is a women's cooperative in Mauritania that is now making green stone beads similar to these beads, from all the stone materials Jamey mentions. They shape the beads individually, using a small portable grinder. They told me that "as young girls they used to make similar beads by rubbing the blanks on hard stone, but why bother when the grinder is so much faster?" (They are advised by a very smart foreign woman who helped them form a cooperative, but I think they are not really targeting the bead collector market. More the tourist market.)

I bought from this cooperative a set of 99 worry beads with separator beads exactly the shape of the pear-shaped multicolored Czech molded beads nicknamed "Mali wedding beads." What caught my eye was that they were working in a chocolate-and-white banded stone, and the result was visually very similar to the black and white striped Mali wedding bead.

Since the Czechs often manufactured and marketed glass imitations of some existing bead that was already popular in Africa (Czech "coral", Czech "lion teeth", etc.), this discovery has me wondering if pear-shape Mali wedding beads were modeled on some other bead already circulating in Africa? Perhaps an earlier version of these Mauritanian beads. If you go 'way back you could make a link with the "breast" beads found in neolithic sites, but I'm fishing for a connection that might have influenced the Czech bead designers in the early 20th century.

The flat triangle-shaped Czech molded beads often mixed in with the pear-shaped Mali wedding beads were modeled on similar stone beads, accoding to Collectible Beads. I bought a few of the Malian stone originals, said to date to the Ghana Empire period. The capital of the Ghana Empire was in south-eastern Mauritania and the empire included territory that is now Mauritanian and Malian. This might lend some credence to my (otherwise blue-sky) theory that the pear-shaped ones are also modeled on beads made in the western sahel.
Any ideas? diplocase