I happened to have this scan at hand, for the work I'm currently conducting. This shows a nicely preserved "Marlik" bead—that we can see remains glassy and light green in tone.

Many "Marlik" beads have become decayed from interment, and have consequently lost most of their color, and have become chalky white and fragile. One of the ways we can tell these decayed beads are glass (were we never to see well-preserved specimens), is to note the structure and decoration. The beads were furnace-wound (which faience would not be), and the decorations are trailed and combed. Faience beads do not normally have conventionally trailed decorations (with some significant exceptions—but these are not "conventional").

Jamey