What form of tea was used as currency in ancient Tibet?

Tea bricks were the form of tea used as currency in ancient Tibet.

Tea was usually traded in compressed blocks called tea bricks, rather than as loose leaves or modern tea bags. The bricks were durable, portable, divisible, and valuable across long-distance trade routes. They could also be brewed or eaten, giving them practical value beyond exchange.

Tea bricks for Tibet were chiefly produced around Ya'an in Sichuan, China, then transported along caravan routes. In Tibet, where locally minted coins were historically less important than barter, tea bricks became a major medium of exchange, especially by the 19th century.

Not every brick had the same value. In the late 19th and early 20th centuries, a common third-quality brick known as brgyad pa was valued at eight Tibetan tangkas in Lhasa. The answer is therefore specifically tea bricks: compressed tea, not ordinary tea leaves or powdered tea.