The Volunteer occurrence area is predominantly underlain by a sequence of weakly bedded, white to mottled grey recrystallized limestone and sandy limestone beds of the Upper Triassic Quatsino Formation. The limestone is intruded by a teardrop-shaped diorite intrusion 1000 metres long and 400 metres wide. Scattered outcrops of thin basaltic flows and breccia also occur.

Magnetite-garnet-diopside skarn has developed adjacent to the diorite/limestone contacts. The skarns appear to be simple replacements along the borders of the diorite and as masses in areas where they are "embayed" by diorite. Gold values are associated with massive magnetite and associated chalcopyrite, which forms the principal mineralization within the skarn. Subordinate pyrite is also evident.

At the Volunteer showing, an embayed skarn is surrounded on three sides by diorite with the thickest zone of magnetite at or very near the nose of the skarnified rock. From the nose of the skarn zone to the portion where diorite lies only to one side, the skarnification wanes to a series of bands of garnet-diopside skarn and marble parallel to bedding. These bands thin out eventually to unaltered limestone. Within the embayed zone of skarn are large patches of massive marble. The best gold and copper values and the highest magnetite content appear to be restricted to the skarn within a few metres of the diorite. Diamond drilling has revealed that considerable epidote occurs on fracture plane surfaces and as a massive flooding in diorite as well as extending into the limestone.

A rock sample of magnetite-garnet skarn assayed 11.65 grams per tonne gold and 20.56 grams per tonne silver (Assessment Report 14814).

In 1924, an 18-tonne shipment of magnetite ore was sent to Seattle for experimental reasons.