This phosphate occurrence is situated on the north side of the Alaska Highway, 1 kilometre north of the confluence of the Tetsa and North Tetsa rivers, about 18 kilometres east of Summit Lake (Fieldwork 1987, Figure 3-7-1, sample locality SB87-41; Open File - Phosphate Deposits in British Columbia).

The deposit is in the Early to Middle Triassic Toad Formation, part of the platformal to basinal sedimentary succession that makes up Ancestral North America (Geological Survey of Canada Map 1713A). The formation is composed of dark grey calcareous siltstone and shale, and minor limestone and very fine grained sandstone (Geological Survey of Canada Memoir 373, Map 1343A). Most lithologies are weakly to moderately carbonaceous. Phosphate-bearing beds occur in the lower and middle parts of the formation, an interval which varies in thickness from a few tens of metres to approximately 290 metres (Fieldwork 1987, page 401; Geological Survey of Canada Bulletin 247).

The Tetsa River West showing consists of two outcrops, about 300 metres apart, of thick-bedded, dark grey siltstone and dolomitic siltstone (Open File - Phosphate Deposits in British Columbia). Bedding strikes 150 degrees and dips 50 degrees northeast. The eastern outcrop contains a 15-centimetres thick bed of phosphorite consisting of 15 to 25 per cent dispersed pellets in a matrix of quartz and minor carbonate. The phosphate is assumed to consist of fluorapatite (Geological Survey of Canada Bulletin 247, page 20). The pellets are subangular to rounded and 0.2 to 0.3 millimetre in diameter. Most have a nucleus of quartz or, less commonly, carbonate; a few have both. In some pellets the phosphate appears to grade into the carbonate nucleus, suggesting replacement of primary carbonate by phosphate. Within the phosphorite bed there is a layer, 5 centimetres thick, in which the volume of pellets reaches 50 to 60 per cent.

At the western outcrop, phosphate occurs as disseminated pellets and nodules in calcareous siltstone. They are 0.5 to 1 centimetre in diameter and their black colour stands out against the dark grey siltstone. Parts of the siltstone are very weakly phosphatic. Dessication cracks and ripple marks were observed at this locality but nowhere else in the area. These features suggest that phosphate deposition took place in a very shallow water environment subject to periodic emergence.