Iron occurrence, Finlayson Lake Area, Rainy River District, Ontario, Canadai

Regional Level Types
Iron occurrence	Occurrence
Finlayson Lake Area	Area
Rainy River District	District
Ontario	Province
Canada	Country

Associated with iron formation exposed on an island in Finlayson Lake. Fenwick, K.G. (1976): Geology of the Finlayson Lake Area, District of Rainy River; Ontario Div. Mines, GR 145, 86p. Accompanied by Maps 2297 and 2298, scale l inch to 1/2 mile (1:31,680).

In September 1943 T.L Tanton examined the newly exposed outcrops of the then
modified Finlayson Lake. Tanton discovered small, bowl-shaped, rusty looking objects growing in an inverted position on the glacially smoothed surface of mineralized graphitic and sericite schists. Tanton called these objects conchilites; the name was derived from two Greek words meaning 'shell' and 'rock'. The conchilites were firmly attached around their edges, and when removed, were found to be filled with liquid vary ing in appearance from clear to turbid, and from colourless to greenish yellow and yellowochre.
Tanton returned in 1944 to obtain samples of this liquid, but though he found many more shells the winter's frost had removed the liquid.
The conchilites occur in the vicinity of mineralized outcrops and are distributed singly, in groups, or in clusters, individual conchilites range in diameter from l inch (2.5 cm) to l yard (0.9 m) and rise above the bedrock from less than l inch (2.5 cm) to more than 3 inches (7.6 cm). The majority of the specimens are shell-shaped, oval or circular with either smooth or irregularly scalloped outlines. A conchilite commonly shows fluted walls. The inner walls vary greatly being sometimes botryoidal, and, some
times composed of glistening crystals of magnetite, covered with soft, powdery manganite.
In addition, there are stalactitic and acicular linings. The conchilites are identified as part of a cell structure The present author noted that conchilites were found mainly in the vicinity of the iron formation and the pyrite showings. They are not only attached to these outcrops,
but are also found cemented to sulphide-barren boulders of metavolcanics that are located beside the iron formation, and pyrite-rich outcrops and erratics. Another interesting feature found on the property of Fin-Lan Copper Mines Limited in the neighbourhood of the iron formation and sulphide showings, is the occurrence of small yellowish brown to 'burnt chocolate' nodules. These nodules are found cemented to, and also rimming, and encrusting the boulders and pebbles in the old sand bottom.
In one case, they were found covering the vertical face of a metavolcanic outcrop. The nodules on this face are in bands, and appear to indicate different water levels.

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References