The Mid Copper prospect is 900 metres northeast of the summit of Boulder Mountain, 2.5 kilometres north of Lockie (Boulder) Creek and 7.5 kilometres north-northwest of Tulameen.
Boulder Mountain is underlain by andesitic to locally dacitic flows and pyroclastic volcanics of the Upper Triassic Nicola Group. These rocks are unconformably overlain along the west flank of the mountain, in the headwaters of Lockie Creek, by felsic to intermediate volcanics of the middle to Upper Cretaceous Spences Bridge Group. The Nicola Group rocks strike north, dip west and are regionally metamorphosed up to greenschist facies.
The deposit consists of a horizon of sulphide mineralization, possibly of volcanogenic origin, hosted in andesitic fragmental volcanics and capped by a massive, white weathering, silicified felsic tuff. The horizon strikes 000 to 023 degrees and dips 21 to 40 degrees west. It has been traced by diamond drilling over a strike length of 90 metres and a dip length of 37 metres. Downdip, a northwest-striking fault displaces the deposit over a vertical distance of approximately 7 metres.
The horizon contains chalcopyrite and pyrite in narrow stratabound to cross cutting sulphide stringers and quartz-carbonate veins, within a zone of pyritized, chloritized, silicified, bleached and sheared andesite (greenstone), 1.5 to 3.0 metres thick. One drillhole analysed 0.31 per cent copper over 1.5 metres (hole 73-5, 9.5 to 11.0 metres), and a second hole, 90 metres north-northwest, analysed 0.21 per cent copper over 1.5 metres (hole 73-7, 0.3 to 1.8 metres) (Property File - L. Sookochoff, 1973, Figure 6). A sample of a quartz-chalcopyrite vein assayed less than 0.07 gram per tonne gold, 2.4 grams per tonne silver, 0.47 per cent copper, less than 0.01 per cent lead and less than 0.01 per cent zinc (Assessment Report 14158, assay certificate, sample R2 BWS Rx 22).
This prospect was initially explored by Gold River Mines Ltd. in 1972 and 1973. The company conducted trenching and 171 metres of drilling in 5 holes. Since then, the deposit has been geophysically surveyed, trenched, mapped and sampled by various operators between 1980 and 1986, and most recently Abermin Corporation.