The Rosa occurrences are located in the southern head waters of Brodick Creek on the northwest corner of Nootka Island, approximately 6.5 kilometres northeast of the community of Nuchatlitz.
The area is primarily underlain by granites and granodiorites of the Jurassic Island Plutonic Suite. To the south east, a small plug of Eocene Catface Intrusions has intruded the granodiorite.
Locally, a complex series of granites and granodiorites hosts two areas of gold mineralization, approximately 40 metres apart, known as prospects A and E.
The E zone consists of a 13.5 metre wide package of sheared, fissile granodiorite hosting five veined zones or brecciated zones. These have been silicified and epidotized with clay and K-feldspar alteration. The veined zones trend 175 to 180 degrees and dip between 65 and 70 degrees to the west. Mineralization is variable, comprised of fine- grained pyrite up to 60 per cent, though generally 5 to 10 per cent overall. Trace amounts of arsenopyrite, chalcopyrite and molybdenite were also noted. In 1990, sampling of hanging wall material from a vein yielded values up to 228.8 grams per tonne gold with other samples yielding between 2.9 to 62.9 grams per tonne gold (Assessment Report 20959).
The A zone consists of pyrite-rich to massive sulphide mineralization, exposed for 135 metres in length and from 6 to 66 centimetres in width, and hosted in a granodiorite. The rock has been variably sheared with pervasive narrow veining and clay and K-feldspar alteration. The mineralized zone trends 160 degrees and dips 45 to 50 degrees to the west. In 1990, chip sampling assayed values from 0.17 to 1.10 grams per tonne gold over 1.0 metre (Assessment Report 20959).
In 1987 through 1990, exploration programs of prospecting, geological mapping, geochemical sampling and trenching were completed.
Previous sampling in the area by McAdam Resources assayed values up to 0.25 per cent copper, 3.5 per cent zinc and 8.8 parts per million silver, but no sample locations were given (Assessment Report 17399).
