It might be more apt to think of Tibetan zi beads as being like other beads that are chemically-decorated agate beads. (The term "etched" is mistaken and voided.)

The tapered bead on the left is a type frequently seen from India and Burma. It is also imitated. I cannot distinguish them from a photo.

On the other hand, the oblate beads have a "carved" appearance that is unexpected. Authentic ancient beads of this type were also made in India, and later in Burma. Take a look at previous posts about "Pyu" and Tircul beads here. These beads also come out of Thailand.

Jamey