The Iva Fern showing is located near the top of the ridge between Cultus and Laib creeks; the veins strike northerly up the slope from Cultus Creek, with the main discovery at about 1905 metres elevation on Lot 12656. The main #2 vein has been traced for over 600 metres along strike; the #1 vein lies 100 metres to the east and is subparallel in strike and has been traced for over 50 metres. Vein widths vary between 0.6 and 2 metres.
Hostrocks belong to the Upper Proterozoic Horsethief Creek Group intruded on the claims just to the west by a small stock of Middle Eocene Coryell biotite monzonite-syenite. Rocks underlying the property have been recently mapped as belonging to the Irene volcanics (greenstone); however, descriptions in old reports mention only slates and shales. The Horsethief Creek Group is known to comprise phyllites, quartzites and grits; regional strike is 010 degrees, dipping 60 degrees west. A basic lamprophyre dike accompanying the vein in places is also described as "hornblendic dyke rock", which might be part of the Coryell intrusions.
Two main fissure veins, containing quartz, siderite, calcite and tourmaline, occur in variably silicified phyllite and slate. Mineralization is in two forms: either coarse galena with pyrite, chalcopyrite and sphalerite, or streaks and bunches of galena and sphalerite. There is significant development of limonite due to oxidation at the surface; outcrops are few, with abundant overburden about 1-2 metres deep covering most of the property.
Grab samples of dump material assay up to 3.5 per cent copper, 26 per cent lead, 9 per cent zinc, 144 grams per tonne silver and 1.4 grams per tonne gold (Minister of Mines Annual Report 1919).
Mapping for Agincourt Explorations Ltd. in 1985 discovered three additional mineralized zones over a total width of 200 metres, concordant with and near the top of the Irene volcanics; the possibility exists that syngenetic sulphides deposited within siliceous sinter zones have been remobilized during metamorphism and nearby intrusion, but this is speculative (Assessment Report 14053). A geochemical survey described in Assessment Report 14053 suggests further mineralization may be buried below overburden to the north, although magnetic and electromagnetic surveys of this area failed to show any significant anomalies/conductors.
Recent work by Yukon Revenue Mines Ltd. resampled old trenches where the best reported sample assayed 1.52 per cent copper, 24 grams per tonne silver and 2 grams per tonne gold across a width of 7.3 metres (George Cross News Letter No. 47, 1994).