I think you will find that the material is serpentine. It is much too soft to be agate or jade.

These beads were artificially patterned to resemble Tibetan zi beads. You bead is plump, but others can be longer tapered beads, and other shapes. It is very typical that the decoration has worn away—to some degree or entirely.

Horace Beck (the founder of modern bead research—and my role model), showed one of these beads in his paper ("Etched Carnelian Beads," 1933), that he proposed was probably Chinese. I don't know that this idea has ever been challenged; nor that any other origin has been proposed. These beads were also shown by David Ebbinghouse, in his multi-part article, "Tibetan dZi Beads," for Ornament, 1982).

Jamey