The Argonaut mine is a massive magnetite-magnetite/garnetite skarn situated on Iron Hill, just east of upper Quinsam Lake.

The skarn is near the contact of limestone of the Upper Triassic Quatsino Formation and an overlying basic volcanic unit of the Upper Triassic Karmutsen Formation, both of the Vancouver Group. The Vancouver Group rocks are intruded by a granodiorite stock of the Early to Middle Jurassic Quinsam intrusions (Island Intrusions). Although the limestone is completely recrystallized, there has been no alteration and the original bedding has been preserved. The basic volcanic package is a sequence of pillow basalts which have been weakly metamorphosed. Locally, the basalts have been hornfelsed near the contact with the granodiorite.

The deposit has been deformed into a west dipping, overturned syncline whose north limb is overturned onto the south limb. The axial plane strikes generally east-west, dips north-northwest, and is irregularly curved along strike. Skarn is best developed and thickest in the hinge portion of the syncline.

Limestone outcrops on surface as an oval shaped body enclosed in skarn and greenstone, trending west-northwest along the synclinal axis for 320 metres, with a width of up to 110 metres. The unit is comprised mostly of massive to thin bedded, medium grained, white to light grey limestone with some thin dark grey beds. The limestone is high calcium in composition, with small grains of pyrite the only visible impurity. A grab sample of chips from blocks of limestone in a dump assayed 98.88 per cent CaCO3, 1.29 per cent acid insolubles, 0.09 per cent total iron and 0.07 per cent total sulphur (Minister of Mines Annual Report 1952, p.224). The Argonaut Co. Ltd. reported a limestone analysis of 54.8 per cent CaO, trace MgO, 0.14 per cent R2O3, 0.6 per cent Fe2O3, 0.06 per cent P2O5 and 0.04 per cent sulphur (Geological Survey of Canada Bulletin 172, p.51).

Skarn mineralization occurs along the contact between limestone and the pillowed basalts and consists of massive garnetite and magnetite with minor amounts of epidote, calcite, and pyrite. The margin of the skarn and host rocks is sharp and irregular. Skarn mineralization rarely occurs outside of the main body and then only as small irregular pods. The skarn mineral assemblage varies from pure, coarsely crystalline massive magnetite at its core to a mixed, crystalline magnetite/garnetite near the margin and a boundary phase of pure crystalline garnetite. In the main body of the skarn, bedding replacement features are present indicating that hydrothermal fluid migration took place preferentially along bedding planes of the limestone. Skarn has preferentially replaced the basalt with respect to the limestone.

From 1951 to 1957, 3,657,168 tonnes of ore were mined, from which 1,990,288,655 kilograms of concentrate was shipped. The dimension of the ore body measured about 400 by 150 by 120 metres, with a strike of 90 degrees and dip of 15 degrees north.

In 2006, sampling of tailing piles yielded:

- 65.9 per cent iron from the upper coarse tailings after concentration

- 20.5 per cent iron from the upper coarse tailings before concentration

- 62.2 per cent iron from the mill site concentrate

- 35.4 per cent iron from the lower coarse tailings

(Assessment Report 28549)

In 1979, a ground electromagnetic survey was completed on the area. In 1988, the area was prospected and sampled by J.P. Loiselle. In 1990, a proposal was underway to recover fine-grained magnetite and garnet from the tailings and waste pile for industrial purposes (D. Hora, personal communication, 1990). In 1995, Aurizon Mines completed a program of rock sampling and a ground electromagnetic survey on the area. During 2006 through 2012, Homegold Resources completed programs of geological mapping, prospecting, sampling of tailing piles and a ground magnetic survey. The magnetometer survey identified a broad high trend to the north west (Assessment Report 33644).