The Rex occurrence is located in the headwaters of a northerly flowing tributary of Cous Creek, approximately 7.5 kilometres west of Dunsmuir Point on the Alberni Canal.
The area is underlain by basaltic flows of the Upper Triassic Karmutsen Formation, Vancouver Group, intruded by swarms of quartz feldspar porphyry dykes. A few outcrops of hornblende diorite of the Jurassic Island Plutonic Suite were observed in the area.
Locally, an area along a creek is composed of intensely pyritized and altered quartz feldspar porphyry dykes and mafic volcanics. The pyrite zone is about 240 metres wide and 1370 metres long. Molybdenite occurs as rosettes and bands in 1.3 centimetre wide quartz stringers within dykes and volcanics. Most of the mineralized material was found within a 60 metre length of the creek. Also, scattered showings of chalcopyrite were reported but considered of minor significance.
In 1967, Amax Exploration completed a program of silt and soil sampling, geological mapping and a ground magnetometer survey on the Rex claims. The grade of the molybdenum was estimated at 0.02 per cent (Assessment Report 1591).
In 1996 through 2006, SYMC resources prospected the area as part of the of the Macktush Property along the west side of the Alberni Inlet, now called the Dauntless property. This work identified an extensive (3 by 5 kilometre) halo of alteration and sulphide mineralization surrounding the showing, including veins of semi-massive chalcopyrite and pyrite mineralization (Assessment Report 28989).
In 2009 through 2011, G4G Resources completed programs of geological mapping and rock and soil sampling on the area as the Macktush Copper property. During 2012 through 2014, Nahminto Resources completed exploration programs including limited prospecting, rock sampling, geological mapping and a satellite remote sensing survey and analysis on the Macktush group. A similar prospecting, geological mapping and rock sampling program was conducted on areas of the Macktush property for World Organics Inc. in 2015.
