The Tlupana Arm (BCD) magnesite/limestone occurrence is located west of Deserted Lake, north of Hisnit Inlet, and east of Head Bay (Tlupana Inlet). The showing is approximately 34 kilometres west of Gold River and is accessed by forestry roads off the Head Bay FSR between Gold River and Tahsis.

The area is underlain by sedimentary and volcanic rocks of the Late to Middle Triassic Vancouver Group (Quatsino Limestone and Karmutsen volcanics and Parson’s Bay sediments). These litholgies are in fault contact with diorites of the Crystalline Westcoast Complex and all lithologies have been intruded, locally, by the Eocene Catface Intrusions.

Locally, the area is dominated by the Upper Triassic Quatsino Limestone. The limestone is in general, massive to thickly bedded and well marbleized. The colour and texture of the limestone are variable from bright white to dark grey, and from fine grained to coarse grained, respectively. The Quatsino formation is moderately dipping at approximately 45 degrees and strikes northwest. Late, fine-grained mafic intrusive dikes of andesite to trachyte cutt the limestone but are, generally, spaced greater than 50 metres apart as identified from geophysical surveys.

About one kilometre southeast of a limestone quarry (Hisnit Inlet - 092E 020) on Deserted Creek are hard, dolomitic bands which contain numerous scattered "spots" up to 5 millimetres in diameter. The spots contain crystals or crystalline aggregates which appear dark on fresh surface. The material is more soluble than the host rock and weathers to a white fibrous residue which is left in cavities or pits on the dolomite surface (Open File 1987-13, page 51).

Goudge (1944) interprets the material to be brucite which is a common component in contact metamorphosed dolomites and which may be fibrous with anomalous birefringence in thin section. Parks (1917) reports similar characteristics for the Tlupana Arm mineral.

From 2006 to 2008, D. Berkinshire completed programs of prospecting and rock geochemical sampling. From 2009 to 2011, Compliance Energy completed programs of geological mapping, geochemical surveys and airborne geophysical surveys.

The TLUPANA ARM occurrence is one of the several industrial mineral showings / quarries within Callache Stone Quarries Inc.'s Tahsis property, including the Nootka Quarry, the CAL A prospect, the CAL B showing and the Century Limestone showing and the Tlupana Arm magnesite showing (Assessment Report 36511).