I recommend my article, “Tibetan Zi Beads: The Current Fascination with Their Nature and History,” Arts of Asia, 32:4, pp. 72 - 91, from 2002.

It is extremely difficult to place even general dates for zi beads. The technology goes back to 2,500 BCE (at Harappa); and some Harappan beads are even among Tibetan/Himalayan beads.

Nevertheless, there were clearly a number of waves of acquisition of beads that became included among zi beads. One can only make comparisons and speculations. For instance, some of the classic (more desirable "pure") zi beads—those that have both darkening of the stone, and conventional chemically-decorated pale decorations, featuring lines and circles—are clearly inspired by what are called "natural zi beads" (that are not chemically decorated). Consequently the classic zi beads would be younger than the beads they imitate. I place the "natural" beads at ca 700 BCE (+ or -). However they or similar beads could be much older. And, the most-likely scenario is that all or nearly all ancient zi beads were made in India (or at least from somewhere where Indian technology was present—as happened in Burma, and resulted in Tircul and pumtek beads).

The problem with chung zi is complicated because, on the one hand similar beads were made in South India. But it is very possible that some (banded or striped beads) may have been made in Germany—and not so long ago. Further investigation is necessary.

In my article I show and describe what I believe are reproduction beads from Idar-Oberstein, Germany, probably made ca. 100 years ago (+ or -). Although these are imitations (or reproductions), they are distinctive enough to be recognized by the unaided eye (by their very translucent coffee-colored Brazilian agate, and other features). Nevertheless, now, Tibetans think of these as "real zi beads," but recognize that they differ from the more-desirable "pure" beads.

I manage an online Yahoo Group called Tibetan Zi Beads. If you join the Group, you will find my article is available via two PDFs; and the photos are posted in the Photos Area. You can find the Group here:

https://groups.yahoo.com/neo/groups/zibeads/info

See also here: http://beadcollector.net/cgi-bin/anyboard.cgi?fvp=/openforum/&cmd=iYz&aK=48889&iZz=48889&gV=0&kQz=&aO=1&iWz=0

Jamey