Alum mountain is significant to the local Worimi Aboriginal people who call it Bulla Della, meaning ‘the Great Rock’. The mountain, a volcanic extrusion, is also known as Alum Mountain, after a rare alunite deposit was discovered there in the late 1800s and subsequently mined until 1952. In 1917, this alunite deposit was reported as one of only 3 known deposits in Australia and the largest deposit in the world.