Being landlocked and high in the Himalayas, most of their beads are imported.

Pema raka from Yunnan.
Amber from Europe.
Coral from Naples (and also China).
Turquoise from Hubei (minorly local).
Zi and other stone beads from India.
Silver and gold work performed by Nepalese smiths.
Mother of pearl--probably mostly from China.
Pearls probably from China and India.

As I have remarked in the past, it is possible Tibetans made beads (as for prayer strands) from natural materials, such as wood and seeds. But possibly even these were imported.

Tibet is not famous for beadmaking. Only for having great beads.

JDA.