The Rex South East occurrence is located on a ridge separating Fosselli and Macktush creeks, approximately 6.5 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 dikes. A few outcrops of hornblende diorite of the Jurassic Island Plutonic Suite were observed in the area.

Locally, a malachite stained, strongly kaolinite altered granitic dike is hosted by weakly epidote and carbonate altered basalt.

In 1996 through 2006, SYMC resources prospected the area as part of the Macktush property along the west side of the Alberni Inlet, now called the Dauntless property. In 2009 through 2011, G4G Resources completed programs of geological mapping and rock and soil sampling on the area as the Macktush Copper property. Samples D055181 and D055182 assayed 0.604 and 0.681 per cent copper, respectively (Assessment Report 32484).

During 2012 through 2014, Nahminto Resources Ltd. 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.