These are made in the environs of India, and I have a collection of them too. There are a number of editions, ranging from well-made and including real turquoise, to sloppy and composed with blue-dyed calcite (or some non-precious stone). The frame of the beads or pendants is usually a cage of silver or brass, filled with dark resin, into which the turquoise bits have been inlaid.

These items have a "Tibetan" feel to them, and it may be that their original home was Ladakh, Kashmir, or Sikkim—or even Nepal. However, as happens in India, it's very likely their manufacture was taken-up in India-proper, for the purpose of making cheaper factory versions (I speculate). They are not exactly common beads, but I would not call them 'rare.' Of course, the well-made specimens that include real turquoise are more desirable than others.

As of about two years ago, a new similar "Tibetan" version of these beads has been made and sold to collectors. While they are frankly new, we should not doubt they will be sold as "antique Tibetan beads." These are either Nepalese or Chinese (I suspect the former).

I hope this helps. Jamey