The perlite occurrence is located south of Ironside Mountain, 2.4 kilometres northeast of Port Louise.

The area is underlain by sub-aerial dacitic to rhyolitic flows and/or domes, with minor breccias and pyroclastics of the Upper Oligocene to Lower Pliocene Masset Formation, which form a plateau volcanic sequence up to 5 kilometres thick dipping gently to the east.

Perlite occurs as a flow-like mass in rhyolite units of the Tartu Facies.

A large gossanous area has zones of argillic alteration, silicification, and pyritization which may reflect the presence of a subvolcanic intrusive. The area was staked in 1986 by City Resources as the Virgo claims and prospected in 1987. No economic mineralization or significant assays were reported (Assessment Report 17053).