The Nimpkish Lake Limestone (Tsulton) occurrence is located east of Nimpkish Lake and approximately 11.5 kilometres south-southeast of the north end of the lake.

A band of limestone of the Upper Triassic Quatsino Formation (Vancouver Group) up to 4.5 kilometres wide trends south-southeast from the north end of Nimpkish Lake for 15 kilometres. The limestone band is bounded to the east by overlying black argillite and limestone of the Upper Triassic Parsons Bay Formation (Vancouver Group). To the west the limestone is conformably underlain by or faulted against basaltic flows of the Upper Triassic Karmutsen Formation (Vancouver Group). A northwest trending mass of coarse grained, biotite quartz monzonite of the Jurassic Island Intrusions truncates the limestone band at its south end.

Mapping and diamond drilling along the east side of Nimpkish Lake, 7.5 to 12.5 kilometres south of its north end, revealed the limestone is comprised of an upper medium to dark grey member with off white to light grey interbeds and a lower white to light grey, generally fine-grained member containing some dark grey and cherty beds. The two members appear to be folded into a broad north trending syncline. Pyritic chert lenses become more frequent southward towards the monzonite intrusion and near the basalt contact. A few thin sills and dykes of fine-grained diabase and silicified and pyritized andesite intrude the limestone.

Various exposures of fine grained, massive, black limestone occur along the Tsulton River, 4 kilometres north of the area mapped in detail. A sample composed of chips taken at 1.5 metre intervals for 48.8 metres along a cut starting 183 metres north of the 6 mile post of the Nimpkish Valley logging railway contained 55.27 per cent CaO, 0.04 per cent MgO, 0.95 per cent insolubles, 0.45 per cent R2O3, 0.06 per cent Fe2O3, 0.009 per cent MnO, 0.03 per cent P2O5, less than 0.01 per cent sulphur and 43.39 per cent ignition loss (Minister of Mines Annual Report 1968, p. 318, Sample 27).

In 2014, 54 Quatsino Formation samples, collected from the occurrence area and up to approximately 3.5 kilometres to the northeast, yielded a wide range of values from 20.63 to 99.54 per cent calcium carbonate, 0.21 to 12.64 per cent magnesium carbonate, and 0.06 to 32.39 per cent silicon dioxide, including 41 samples yielding values greater than 95 per cent calcium carbonate with the best section (2014-01) averaging 96.49 per cent calcium carbonate, 2.63 per cent magnesium carbonate and 0.54 per cent silicon dioxide over 17 metres (Assessment Report 34923).

In 2017, 43 Quatsino samples collected from the Nimpkish property (MINFILES 092L 186 and 092L 349) were highly variable in quality, ranging from 78.35 to 99.68 per cent calcium carbonate, 0.36 to 4.96 per cent magnesium carbonate and 0.05 to 10.21 per cent silicon dioxide (Assessment Report 37354).

In 2018, 70 Quatsino samples collected from the Nimpkish property (MINFILES 092L 186, 092L 349 and 092L 360) were highly variable in quality, with the highest quality section (2018-02) averaging 98.05 per cent calcium carbonate, 0.42 per cent magnesium carbonate and 0.71 per cent silicon dioxide over 18.25 metres and another notable high-quality section (2018-04) averaging 98.19 per cent calcium carbonate, 0.49 per cent magnesium carbonate and 0.69 per cent silicon dioxide over 12 metres (Assessment Report 38082).

Work History

Industrial Fillers Ltd. staked a large portion of the limestone band in 1987. Mapping and diamond drilling were conducted by the company in 1988 to assess the deposit for its white coloured limestone. In 2000 and 2001, Homegold Resources completed a program of geological mapping and two diamond drill holes, totalling 51.8 metres, on the area as the Smiley 1-6 claims. During 2007 through 2009, Graymont Western Canada completed programs of rock sampling and geological mapping on the area as the Nim 1-18 claims. In 2010, Homegold Resources prospected the area immediately northwest as the Smiley W claim. During 2010 through 2019, Graymont Western Canada Inc. completed programs of prospecting, geological mapping, rock sampling and 561.8 line-kilometres of ground magnetic surveys on the area as part of the MQ, Nimpkish, Varney Bay and Bonanza properties.