The area is underlain by cherty tuff, crystal tuff and thin- bedded sediments of the Mississippian to Pennsylvanian Fourth Lake Formation, Buttle Lake Group (formerly the Sediment-Sill Unit of the Sicker Group). The area is intruded by sills and dykes of diabase and gabbro (informally known as the Mount Hall Gabbro) that are coeval with the Upper Triassic Karmutsen Formation, Vancouver Group.

The Hollings rhodonite deposit consists of a lens, convex at top and bottom, reaching a maximum thickness of 5 metres and a minimum length of 30 metres. The banded variety contains abundant quartz, jasper and minor amounts of spessartite. Rare fragments of green chert host rock are present in the rhodonite. Rhodochrosite surrounds calcite veins and bands. There are numerous quartz, minor rhodonite and minor neotocite veins cutting the rhodonite.

The lower 25 centimetres of the rhodonite lens consists of interbeds of rhodonite and calcareous magnetite-garnet schist, followed by a 9.5-metre sequence of argillaceous metachert, cherty crystal tuff with idiomorphic garnet and minor recrystallized limestone. Directly up section from the rhodonite lens is a 0.5- metre band of argillaceous garnet-magnetite metachert. Still further upsection an igneous intrusion (unspecified type) has obliterated the section. Glacial drift and alluvium cover the sequence further down section.

The rhodonite is considered to be of excellent gem quality and the deposit has been quarried commercially on a small scale. The material is sold in chunks of various sizes, by the pound or in sawed blocks and slabs. Most of the production has been sold in rock shops for amateur use and no figures are available.

Fred Hollings mined the deposit in the 50's and 60's.