The Grunwald area is underlain by a sequence of Jurassic clastic and volcanic rocks of the Hazelton Group which trend north to northwest and are intruded by felsic stocks and dikes and/or sills to the west. The area is dominated by a major anticline, which displays eastern vergence. Reddish to maroon andesitic volcaniclastic and volcanic rocks of the Betty Creek Formation are located close to the anticline’s axial plane. To the west and east of the anticline’s axis there are felsic rocks of the Mount Dilworth Formation(?). They form a horizon, 70 to 200 metres wide, composed of apple green, light grey or white coloured felsic volcanic rocks which include flows, intrusions and pyroclastic rocks. Large gossans are related to sericite alteration and subsequent infusion of quartz and sulphide mineralization and it is speculated that the alteration is associated with the abundant intrusive rocks in the area. In these sericitic zones it is very difficult to differentiate between altered intrusive and felsic volcanic rocks.

Hostrocks in Grunwald area consist of grey, fine grained to glassy appearing rhyolites. West of the rhyolites, a sequence of black argillites is interbedded with grey andesitic tuffs and flows. A belt of northerly trending, maroon pyroclastic rocks and flows is also present; included in this sequence are crystal lithic tuffs, tuff breccia, coarse lapilli tuffs and thin beds of ash and fine lapilli tuff.

In 2017, about 22 rock samples, both grab and float, were collected just east of the toe of Grunwald Glacier, including significant outcrop grab samples DM126 to 129, DM131 and 132 and A17-131 (Figure 4B, Assessment Report 37453).

Sample DM127 was taken from a narrow but prominent shear with a 15-centimetre quartz vein hosting small amounts of pyrite and chalcopyrite. This sample assayed 25.3 grams per tonne gold and 210 grams per tonne silver and 1.79 per cent copper, 6.94 per cent lead and 1.71 per cent zinc (Assessment Report 37453). Sample DM132, taken from a quartz vein (about 100 metres northwest of DM127) with discontinuous bands of pyrite, chalcopyrite, galena and sphalerite assayed 1.65 grams pre tonne gold, 171 grams per tonne silver, 0.31 per cent lead and 3.35 per cent zinc (Assessment Report 37453). Sample A17-132 was collected from a 0.3 to 0.5-metre-wide layer of weathering brown mudstone/limestone hosting minor sphalerite and galena; the sample yielded 10.6 grams per tonne silver, 0.14 per cent lead and 0.89 per cent zinc (Figure 4B, Assessment Report 37453). Grab sample A17-132 was located approximately 100 metres east-southeast of Sample DM127.

Sampling in the Grunwald Glacier area was done in 2005 by Pinnacle Mines and in 2016 and 2017 by Mountain Boy Minerals. See Ataman (104A 179) for details of the Surprise Creek property, of which the Grunwald showing is part of.