The Cusker claims, part of the Bertha project, are located 12 kilometers north of Robb Lake, on Sidenius Creek.
Regionally, a Lower and Middle Devonian platformal carbonate sequence consists of two assemblages. The lower assemblage comprises the Upper Silurian and Lower Devonian Muncho-McConnell and Lower and Middle Devonian Stone formations. These are almost entirely comprised of dolomite with various admixtures of quartz sand or sandstones and argillaceous dolomite. The upper assemblage, comprising the Middle Devonian Dunedin Formation, consists of dolomites or variably dolomitized limestones. The Lower and Middle Devonian sequence lies disconformably on Lower Silurian carbonates of the Nonda Formation and is overlain by basinal shales of the Upper Devonian-Lower Carboniferous Besa River Formation.
Mineralization consists of galena and minor sphalerite in small veins in a fine-grained dolomite; copper has also been noted in more siliceous veins.
The Bertha project identified seven zinc zones with two exceeding 1000 parts per million zinc plus two silver anomalies on the Cusker claims (Property File Cyprus Anvil Campbell, N., 1972).
In 1973, two rock samples (6519R and 6520R), taken from a ridge, yielded 0.40 per cent zinc each with 9.0 and 3.5 grams per tonne silver, respectively (Assessment Report 4203).
In the early 1970s, following the discovery of the Robb Lake (Barrier) prospect (MINFILE 094B 005), Brinex Limited completed regional geochemical sampling of the Lady Laurier and Robb lakes area. In 1972, General Resources Ltd. completed a program of geological mapping on the area as the Tye claim. The following year, British Newfoundland Exploration Ltd. completed a program of geological mapping and geochemical (rock, silt and soil) sampling on the area as the Brin, JR, Lau and Toll claims. Also at this time, Buckhorn Mines Ltd. completed a program of soil and silt sampling on the area immediately west of the occurrence as the Dave and Doug claims.