The Ruby Mountain Magnesite occurrence is located on the western flanks of Ruby Mountain about 22 kilometres northeast of the community of Atlin.

The Ruby Mountain area is underlain by Mississippian to Triassic Kedahda Formation (Cache Creek Complex) sediments and Upper Mississippian to Permian Nakina Formation (Cache Creek Complex) mafic volcanics. These are intruded by Upper Mississippian to Permian Cache Creek Complex ultramafic rocks, and alaskite of the Late Cretaceous Surprise Lake batholith (Surprise Lake Plutonic Suite). The eastern flank of the mountain is overlain by Tertiary-Quaternary olivine basalt and scoria.

Small, brown weathered outcroppings of magnesite are reported to occur in the drainage basins of Ruby, Birch and Boulder creeks which drain into the western portion of Surprise Lake. The larger showings often host quartz veins and/or disseminated pyrite. Documentation of specific locations and geological character is poor.