Beads such as these were made from a Chinese version of faience (also called "composition" or "paste" by some writers).

Terra-cotta is a red clay of fairly coarse texture, used in common pottery functions.

In contrast, Faience-making would have been introduced into China in the Warring States Period (as was glassmaking), from the Mediterranean. Faience is made from ground-up quartz dust (and is therefore very different from clay). The external patterns seen on Chinese faience beads are "glaze," or actual colored glass.

In all likelihood, the dates of these beads are not as early as Steve suggests. I would guess that the glass beads (may) predate the faience beads, judging by comparing them to one another, and noting that some glass beads (not so many) and some faience beads (rather more numbers) share a similar design style that suggests some probable evolutionary development. Specifically, the eyes that are found inside squares or diamonds (squares positioned with a corner up, down, left, and right).

Jamey

P.S. I'm a year older than Steve, and a "rabbit."