The Swannell River limestone occurrence is located on the north side of Swannell River, just west of Orion Creek, about 108 kilometres north-northwest of the community of Germansen Landing.

Regionally, the area is underlain by a series of northwest trending sedimentary rocks of the Neoproterozoic Ingenika Group and include argillite, greywacke, wacke and conglomerate turbidites of the Swannell Formation, mudstone, siltstone, shale and fine clastic sedimentary rocks of the Tsaydiz and Stelkuz formations and limestone, marble and calcareous sedimentary rocks of the Espee Formation. To the southwest volcaniclastic rocks of Permian age and fine clastic sedimentary rocks of Mississippian to Pennsylvanian age, both of the Lay Range Assemblage are exposed.

Neoproterozoic Ingenika Group limestones outcrop along the northeast side of Swannell River for 2500 metres, just west of Orion Creek. The strata strikes 135 degrees and dips 35 degrees southwest on the southwest limb of a northwest-trending anticline cored by underlying schist, slate, and phyllite of the Ingenika Group.

At 1250 metres above the base of the Ingenika Group, the limestone is ivory-buff to rose-yellow coloured and poorly bedded to slaty with very thin sericitic and chloritic partings. In 1954, an analysis of a grab sample yielded 49.24 per cent CaO, 0.36 per cent MgO, 9.50 per cent insolubles, 1.08 per cent Al203 plus Fe2O3, 38.78 per cent CO2 and 0.68 per cent water (Geological Survey of Canada Memoir 274, page 68, Sample 204R).

Up section 366 metres, the rock is comprised of pale green and silver-buff, banded, sugary textured, micaceous limestone containing numerous sericitic flakes and a few scattered grains of detrital quartz. The matrix consists of sheared, medium-grained recrystallized calcite. In 1954, a grab sample analysis yielded 38.42 per cent CaO, 2.60 per cent MgO, 22.34 per cent insolubles, 3.86 per cent Al2O3 plus Fe2O3, 31.64 per cent CO2 and 1.88 per cent water (Geological Survey of Canada Memoir 274, page 68, Sample 203R).