The Port McNeill occurrence outcrops about 4 kilometres southeast of Port McNeill on a northward flowing tributary of Hyde Creek.
A mass of limestone of the Upper Triassic Quatsino Formation (Vancouver Group) is exposed as a west trending lens shaped mound at least 1.6 kilometres long and 800 metres wide on both sides of the creek. The mass is situated near the northeast corner of a 10 kilometre long triangular fault block comprised essentially of the Upper Triassic Parsons Bay Formation (Vancouver Group) and the Lower Jurassic Bonanza Group (Geological Survey of Canada Map 1552A). To the east the limestone is observed to rest on underlying amygdaloidal and porphyritic basaltic lavas of the Upper Triassic Karmutsen Formation (Vancouver Group). To the south the limestone is in fault contact with these volcanics. Bedding in outcrops to the west strikes 051 to 055 degrees and dips 47 to 60 degrees northwest. Drilling in 1980 revealed the limestone is at least 60 metres thick.
The deposit consists mostly of well-jointed, fine-grained, light grey to white banded limestone with occasional dark patches and bands. The darker material becomes more common in the eastern portion of the deposit. Exposed surfaces display siliceous fossil remains(?) weathering out of the limestone. The limestone is pyritic in a few instances. In thin section the rock displays sparsely scattered quartz grains in fine grained calcite. A quarry just west of the creek reveals the limestone is intruded by several andesitic dykes 0.3 to 1.5 metres wide and a mass of serpentinite 23 metres in diameter.
A sample comprised of chips taken at 0.30-metre intervals across 18.0 metres of quarry face contained 53.64 per cent CaO, 0.22 per cent MgO, 3.10 per cent insolubles 0.33 per cent R2O3, 0.17 per cent Fe2O3, 0.015 per cent MnO, 0.02 per cent P2O5, 42.49 per cent ignition loss and 0.20 per cent water (Minister of Mines Annual Report 1968, p. 318, Sample 21). A grab sample of randomly collected chips from the quarry floor contained 55.26 per cent CaO, 0.08 per cent MgO, 0.92 per cent insolubles, 0.12 per cent R2O3, 0.06 per cent Fe2O3, 0.003 per cent MnO, 0.03 per cent P2O5, 0.01 per cent sulphur, 43.43 per cent ignition loss and 0.11 per cent water (Minister of Mines Annual Report 1986, p. 318, Sample 18). A 244 by 244 metre block encompassing the quarry is estimated to contain 5.4 million tonnes of limestone down to a depth of 18 metres below the quarry floor (Assessment Report 10193, p. 6).
In 2015, nine samples yielded from 95.65 to 99.15 per cent CaCO3, 0.23 to 0.98 per cent MgCO3 and 0.37 to 3.22 per cent SiO2 from a 12.5 metre section of Quatsino Formation limestone (Assessment Report 35989).
Work History
This deposit was quarried by Lamac Construction Ltd. during 1967 and 1968 for riprap for a breakwater at Port McNeill. The rock broke into pieces too small for this use, because of the extensive jointing, bringing the operation to an eventual halt. International Marble and Stone Company carried out 499 metres of diamond drilling and some geological mapping in 1980 and 1981. Industrial Fillers Ltd. staked the deposit in 1987 and geologically mapped the northeastern extension of the deposit in 1988, while exploring for white limestone. No production figures are available. During 2015 through 2019, Graymont Western Canada Inc. completed programs of geological mapping, rock sampling and 34.7 line-kilometres of ground magnetic surveys on the area as the Kilpala and Cluxewe claims.
