The Mex occurrence is located on a northwest-trending ridge southeast of the Finlay River, approximately 3 kilometres northwest of Giegerich Peak, and about 280 kilometres north of the community of Smithers.

Regionally, the area is situated within a Mesozoic volcanic arc assemblage, which lies along the eastern margin of the Intermontane Belt, a northwest-trending belt of Paleozoic to Paleogene sediments, volcanics and intrusions bounded to the east by the Omineca Belt and to the west and southwest by the Sustut and Bowser basins.

The oldest rocks exposed in the region are Permian Asitka Group crystalline limestones, which are commonly in thrust contact with Upper Triassic Stuhini Group andesite flows and pyroclastic rocks, and marine sedimentary and volcanic rocks of the Lower to Middle Jurassic Hazelton Group. These rocks have been intruded by plutons and other bodies of the mainly granodiorite to quartz monzonite Early Jurassic Black Lake Suite and are in turn unconformably overlain by, or faulted against, Lower Jurassic calc-alkaline volcanics of the Toodoggone Formation (Hazelton Group).

The dominant structures in the area are steeply dipping faults that define a prominent regional northwest structural fabric trending 140 to 170 degrees. In turn, high angle (approximately 60 degrees), northeast-striking faults appear to truncate and displace northwest-striking faults. Collectively these faults form a boundary for variably rotated and tilted blocks underlain by monoclinal strata.

The Mex occurrence area is underlain by dacitic lithic crystal, lapilli and ash flow tuff of the Lower Jurassic Toodoggone Formation of the Hazelton Group. The Toodoggone Formation is intruded by granodiorite, quartz monzonite and quartz diorite of the Giegerich pluton of the Early Jurassic Black Lake Intrusive Suite and potassium-feldspar phyric dacite, monzonite and monzodiorite dikes. The contact zone forms a prominent gossan along a ridge and extending across the ridge down into the adjacent valleys approximately 1000 metres to the northeast and southwest. The monzonite dikes that intrude dacitic tuffs strike dominantly northeast parallel to the main intrusive contact and the gossan zone of alteration and mineralization. A major north-northeast striking, vertically dipping fault was interpreted to exist between the altered, gossanous monzonite and the unaltered granodiorite of the Giegerich pluton.

Alteration of the intrusions underlying the Mex occurrence consists of moderate to strong propylitic alteration and silicification. Replacement of mafic minerals by epidote and chlorite varies from greater than 50 per cent in the west, decreasing to less than 50 per cent in the east. Silicification consists of, from east to west, minor quartz veining and blebs, to veining up to 3 millimetres wide with irregular spacing and occupying up to 80 per cent by rock volume. A northwest-trending gossan crops out for approximately 1000 by 500 metres along a ridge immediately to the northwest of the Mex occurrence. Jarosite and limonite occur as fracture coatings, clots and disseminations.

Two gold-bearing intrusions have been recognized at the Mex occurrence. One is a pyritic (up to 7 per cent) and silicified quartz monzonite phase and the other is a monzonite with 0.5 to 10 per cent magnetite.

Mineralization consists of spotty patches of disseminated and fracture-controlled chalcocite and lesser chalcopyrite over an area of approximately 400 by 250 metres. Both minerals are very fine grained and rarely comprise more than 0.25 per cent rock volume. Neoticite, pyrolusite, malachite, azurite and chrysocolla are also commonly found as fracture coatings. Pyrite and/or magnetite are very common, ranging from 0.25 to 10 per cent in modal abundance and averaging 1 per cent. Massive slabs of magnetite occur associated with fault zones. The occurrence is reported to be a calc-alkaline copper-gold porphyry deposit.

Initial exploration of the Mex occurrence occurred in 1977, when Cominco Limited staked claims in the Toodoggone area, which included the Mex occurrence. Cominco carried out an exploration program consisting of reconnaissance geological mapping and geochemical sampling (rock chip and soil sampling). Rock samples yielded values up to 0.091 per cent copper, 4.3 grams per tonne silver, 0.005 per cent molybdenum and 0.780 gram per tonne gold (Assessment Report 6763).

In 1981, Cominco re-analyzed soil samples from the 1977 exploration program to assess the gold and silver potential of the property. Additional rock and soil samples were taken to test reproducibility and the extent of gold anomalies. At this time, 10 rock chip samples were taken, mostly from the alteration zone. All but two samples yielded enrichment in gold, from 0.010 to 0.168 gram per tonne. Multi-element geochemistry was completed on only 4 samples, all from monzonite. All were anomalous in copper (0.0195 to 0.1456 per cent) and weakly anomalous in silver (1.2 to 2.6 grams per tonne) and molybdenum (0.0010 to 0.0047 per cent; Assessment Report 9384). Sample 81MRT-4 yielded 0.0068 gram per tonne gold, 2.6 grams per tonne silver, 0.1456 per cent copper, 0.0099 per cent lead, 0.0199 per cent zinc and 0.0010 per cent molybdenum, the highest assay values for all elements except gold and zinc: (Assessment Report 9384). Cominco dropped the property in 1984 because of its low potential for gold mineralization. In 1986, D.L. Cooke compiled a summary report on the work completed on the Mex property. Cooke also collected rock samples from the property. The Eric claim, part of the larger Eric Group property, was recorded in February 1986. This claim contains what was previously known as the Mex claim. The Eric Group property was optioned to Canadian Ventures Corporation in 1987. In 1988, approximately 50 line kilometres of airborne magnetic and very low frequency electromagnetic surveys were conducted over the Eric and Dawn claims for Canadian Ventures Corporation.

In 1991, the Eric claims lapsed and Cominco renewed its interest in the area by staking the Mex property (Paula claim). In the same year, Cominco conducted a reconnaissance program consisting of geological mapping and geochemical sampling (soil, silt, moss mat and rock chip). The program confirmed the existence of copper-gold porphyry mineralization over a large area. Rock samples yielded up to 0.146 per cent copper and 1.932 grams per tonne gold (Assessment Report 22240).

In 1996, Electrum Resources obtained control of the property and was included in the Stealth Minerals Ltd.-Electrum Resources joint venture later that year. In 1998, Stealth Mining Corporation (later known as Stealth Minerals) conducted a preliminary evaluation of the Mex occurrence, which included geological mapping and taking rock samples from the crest of the ridge. Ten rock samples yielded from 0.007 to 0.292 gram per tonne gold with 0.002 to 0.627 per cent copper (Assessment Report 25908).

In1999 and 2000, Stealth Mining completed further programs of geological mapping and rock and soil sampling on the area. Rock samples, taken in 2000, yielded up to 0.60 gram per tonne gold, 1.7 grams per tonne silver, 0.096 per cent copper and 0.016 per cent molybdenum (Assessment Report 26545).

Geological mapping, prospecting, rock sampling, and ground induced polarization and magnetometer surveys were completed by Stealth Minerals in 2002. This program yielded anomalous assay values for gold, silver, copper, zinc and molybdenum with grab samples yielding up to 0.25 per cent copper and 0.29 gram per tonne gold (Assessment Report 27160). The results of the geophysical survey indicate a strong magnetic high with an isolated chargeability and resistivity high, which may represent a body dipping steeply to the northwest.

In 2004, Cascadero Copper acquired the Toodoggone project, which included the Mex occurrence. In 2005, a helicopter-supported diamond drill program was completed. A total of 989.6 metres were drilled in five BTW-size diamond-drill holes, yielding intercepts of up to 0.180 per cent copper with 0.367 gram per tonne gold over 32.0 metres and 0.048 per cent copper with 1.745 grams per tonne gold over 7.4 metres at the end of hole MX05-01, and 0.011 per cent copper, 0.180 per cent zinc and 0.162 gram per tonne gold over 16.1 metres at the end of hole MX05-02 (Assessment Report 28071).

On March 6, 2009, Gold Fields Toodoggone Exploration Corporation and Cascadero Copper Corporation entered into an option and joint-venture exploration agreement. A small surface sampling program including 16 rock, 11 stream sediment and 16 talus fines samples was conducted in 2009. A program of rock and silt sampling, geological mapping, a 180-line kilometre ground induced polarization survey and a 2778-line kilometre airborne magnetic survey were completed on the area. In 2010, a total of 59 talus fines samples were collected along the Mex Ridge. In 2011, Gold Fields Toodoggone Exploration Corporation conducted a drill program at the Mex occurrence, part of the Toodoggone project, under option from Cascadero Copper Corporation. A total of 2477.9 metres were drilled in seven holes. The purpose of the 2011 exploration program, which consisted of diamond drilling, was to investigate the porphyry potential of the Mex occurrence by following up on porphyry indicators such as geophysical and gold and copper geochemical anomalies discovered along the northeast slope of the Mex Ridge in 2009 and 2010, the prominent oxide cap and the mineralization encountered at depth in during the 2005 drill program. A total of 36 rock samples were also collected. Anomalous gold and copper were found in all the drillholes; however, mineralization tends to decrease to the northeast. As evidenced by the prominent gossan zone on the Mex Ridge, significant copper is not found in the upper portion of all the drillholes because it has been leached away. Drillholes MEX11-01 and MEX11-02 have the greatest occurrence of gold and copper whereas MEX11-04 and MEX11-06 have an increase in molybdenum associated with a decrease in gold and copper at depth within the granodiorite. Drilling intercepts included 0.241 per cent copper with 0.183 gram per tonne gold over 87.5 metres and 0.100 per cent copper with 0.269 gram per tonne gold over 132.3 metres in hole MEX11-01, and 0.406 gram per tonne gold over 35.0 metres in hole MEX11-02 (Assessment Report 33018).

In 2012, Cascadero Copper Corporation drilled seven holes totalling 2190.2 metres on the Mex property to test a magnetic anomaly and explore deeper (to 332 metres). Hole MEX12-008 showed early-stage magnetite-biotite-quartz veins overprinted by pervasive phyllic alteration with gypsum, laumontite and late calcite veins. Copper mineralization may be transitional between the potassic alteration and phyllic overprint stages. Drilling intersected lithic-crystal tuff and latite dikes of the Lower Toodoggone Formation, and monzonite to monzodiorite intrusive with minor quartz-sulphide veinlets. A 16-metre intersection assayed 0.424 gram per tonne gold and 0.124 per cent copper, whereas other drill intercepts included 3.335 grams per tonne gold with 0.067 per cent copper over 7.00 metres in hole MEX12-009, 0.856 gram per tonne gold with 0.076 per cent copper over 4.00 metres in hole MEX12-010, 0.119 gram per tonne gold with 0.315 per cent copper over 4.00 metres in hole MEX12-011, and 0.236 gram per tonne gold with 0.160 per cent copper over 8.00 metres in hole MEX12-012 (Assessment Report 33802).

During 2016 through 2018, Amarc Resources Ltd. completed programs of soil and rock sampling, geological mapping, 115.0 line kilometres of ground induced polarization surveys and 1940.0 line kilometres of airborne magnetic surveys on the area as the Joy property. In 2018, six rock samples (743355 to 743360) from the area assayed from 0.152 to 0.514 gram per tonne gold (Assessment Report 38201).

Refer to Pine (094E 016) for further details of the Pine property geology and work history. The Mex occurrence was part of the Pine and later the Joy properties.