The Nimbin Rocks are volcanic extrusions of rhyolite

Rhyolite

This page is about a volcanic rock. For the ghost town see Rhyolite, Nevada, and for the satellite system, see Rhyolite/Aquacade.Rhyolite is an igneous, volcanic rock, of felsic composition . It may have any texture from glassy to aphanitic to porphyritic...

 left over from the Mount Warning

Mount Warning

Mount Warning is a mountain west-south-west of Murwillumbah, near the border with Queensland in the Northern Rivers region of New South Wales, Australia...

 Tweed Volcano

Tweed Volcano

Tweed Volcano was an early Miocene shield volcano in northeastern New South Wales, Australia. In the course of about three million years, Tweed Volcano was formed over the East Australia hotspot when this part of the continent passed over it around 23 million years ago...

 that erupted around 20 million years ago in what is now northern New South Wales

New South Wales

New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...

, Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

.

As part of an eroded dyke of the volcano, the Rocks are situated just outside the present day caldera

Caldera

A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...

 wall about 20 km from Mount Warning and three kilometres from Nimbin

Nimbin, New South Wales

Nimbin is a village in the Northern Rivers area of the Australian state of New South Wales, approximately 30 km north of Lismore, 33 km southeast of Kyogle, and 70 km west of Byron Bay....

 village. The three most prominent were named by early white settlers as the Thimble, Cathedral and Needle. They are an extremely significant cultural site to the local Bundjalung tribe of indigenous Australians

Indigenous Australians

Indigenous Australians are the original inhabitants of the Australian continent and nearby islands. The Aboriginal Indigenous Australians migrated from the Indian continent around 75,000 to 100,000 years ago....

 who believe the rocks were home to the Nmbngee, or Clever Men. They were also initiation grounds for young boys and the dreaming story can be read at the Nimbin Museum.