The Osilinka River limestone occurrence is centred on a ridge crest north of Osilinka River, east of Tenakihi Creek, approximately 48 kilometres northwest of the community of Germansen Landing.

A thick limestone member of the Neoproterozoic Espee Formation (Ingenika Group) outcrops as a 1000-metre-wide band extending north-northeast from the Ingenika River for 3000 metres, where it is truncated by a fault. The limestone and enclosing schist, slate and phyllite strike north and dip 30 to 40 degrees west.

The limestone, on the crest of a ridge north of the Osilinka River just east of Tenakihi Creek, is pale purple and buff grey, fine-grained and poorly bedded. In 1954, a sample from about the middle of the limestone member analyzed 54.32 per cent CaO, 0.51 per cent MgO, 2.30 per cent insolubles, 0.77 per cent Al2O3 and Fe2O3, 41.14 per cent CO2 and 1.58 per cent water (Geological Survey of Canada Memoir 274, page 68, Sample 23R).

A sample (ca. 1954) of ivory coloured, granular limestone taken on the east side of Tenakihi Creek valley, just north of the Osilinka River, analyzed 48.86 per cent CaO, 0.34 per cent MgO, 8.50 per cent insolubles, 2.44 per cent Al2O3 and Fe2O3, 39.20 per cent CO2 and 0.72 per cent water (Geological Survey of Canada Memoir 294, page 68, Sample 33W). The limestone contained abundant muscovite flakes up to 1 millimetre long. This sample was taken 120 metres stratigraphically above the previous sample. Beds of limestone in this vicinity have been locally replaced by siderite.