Pearl shells were used in rain-making ceremonies by Aboriginal groups across Central Australia. The zigzag-shaped lines carved into some of the shells represent sheets of lightning associated with storm clouds, and the dots between the lines are droplets of rain. The anthropologist C P Mountford recorded a ritual ceremony conducted by the Pitjantjatjara people in which similar shells were used in a successful attempt to produce rain. The shells generally originated in Broome, Western Australia, and were highly prized objects of trade. Some examples have been found as far afield as Port Augusta in South Australia. This Bardi incised pearl shell was made in the early 1920s.