The Rex showing comprises a dual system of veins outcropping in argillite of the Helikian Aldridge Formation, Purcell Group.

Vein No. 1 strikes at 115 degrees (with an apparent dip of 70 degrees southwest) while Vein No. 2, “a series of quartz stringers stockworking with Vein No.1”, strikes 042 degrees with “almost” vertical dip. Strong copper mineralization was reported in Vein No.1 hand specimens, consisting of chalcopyrite and cuprite with malachite and azurite. A random grab sample was reported to have yielded 2.39 per cent copper, 58.29 grams per tonne silver and 0.34 gram per tonne gold; a selected chalcopyrite sample from the shaft, taken in 1995, was reported to have yielded a high gold value (Exploration Report for Gallowai Metal Mining Corporation, September 22, 1997, Property File Document (PFD 676699).

In 1992 a helicopter borne DIGHEM survey over the Balsam, Cedar, and Dogwood claims of R.H. Stanfield (Bul River Mineral Corporation Ltd.) was completed (Assessment Report 23012). In 2017, an NI43-101 technical report for Purcell Basin Minerals Inc. defined exploration targets peripheral to the copper ore body on the Bull River Mine property (Assessment Report 37195). This work was facilitated by the processing of Dighem airborne EM (AEM) data acquired from 1991-1997 surveys. Processing and interpretation of the historic Dighem data identified several target areas of coincident EM and magnetic features. Figures 7, 8 and 9 show magnetic and resistivity coverage from the Bull River mine area southeast to the Elko community area (Assessment Report 37195).

In 2019, five NQ2 diamond-drill holes were completed Braveheart Resources Inc. on the Rex zone structure for a total of 1196.33 metres (Assessment Report 39163). Several of the holes intersected significant core lengths of strong siderite-quartz-pyrrhotite veining with minor chalcopyrite. Veining exists principally as sheet veins and some stockwork. Pyrrhotite is the dominant species with subordinate pyrite and minor chalcopyrite. The vein zones are accompanied by sericite plus/minus chlorite alteration. Thus, vein zones represent both a structural and hydrothermal corridor. Despite intersecting significant zones of mineralized structure, the drilling did not produce any economical grades.

In 2018, Purcell Basin Mineral completed geological mapping, geochemical surveying, and geophysics on the Rex Zone (Assessment Report 37983).

Refer to Mountain (Dean) (082GNW047) for related mineralization details and Bull River (082GNW002) for details of the greater Bull River property which contained the Rex zone and 25 other MINFILE documented mineral occurrences (as of October 2022).