The A25 occurrence is located at an elevation of 560 metres on a north-flowing tributary of the Artlish River referred to as Toray Creek, approximately 14.5 kilometres east of the Artlish River mouth on Tahsish Inlet.
Regionally, the area lies within a broad northwest-trending sequence of interbedded sediments and volcanics of the Upper Triassic to Lower Jurassic Parson Bay Formation (Bonanza Group) and Upper Triassic Quatsino Formation (Vancouver Group). This assemblage lies on the northeastern flank of the extensive granodiorite Zeballos intrusion phase of the Jurassic Island Plutonic Suite.
Locally, gold-magnetite occurrences lie within a belt of magnetite occurrences that extends from Zeballos River for approximately 10 kilometres in a northwest direction. The mineralization occurs at or near the conformable contact between Quatsino Formation crystalline limestone and both the overlying highly altered and folded Parson Bay Formation volcanic and sedimentary rocks and the Lower Jurassic Bonanza Group.
At the A25 occurrence, a sequence of alternating andesitic pyroclastics and limy argillites of the lower Bonanza Group trends 158 degrees and dips 45 degrees southwest. Extensive dacitic to rhyolitic dikes are present. Diorite is present nearby. Intruded rocks are extensively amphibolite and skarn altered. The pyroxene skarn zones contain primarily disseminated to massive pyrrhotite and magnetite mineralization with associated and sporadic pyrite, chalcopyrite, tellurobismuthite and native gold. The gold-bearing magnetite skarn is approximately 110 metres thick.
In 1980, a sample (697-15) assayed 3.15 grams per tonne gold and 3.42 grams per tonne silver (Assessment Report 8612).
In 1984, chip sampling yielded up to 15.07 grams per tonne gold over 2 metres (samples 26895 and 26896), whereas another chip sample, taken 25 metres to the north of the previous, yielded 4.38 grams per tonne gold over 1.0 metre (Assessment Report 13665). Other chip samples, taken approximately 150 metres to the south, yielded up to 8.97 grams per tonne gold over 1.0 metre, with adjacent samples yielding 7.60 and 4.08 grams per tonne gold over 0.5 and 0.3 metre, respectively (Assessment Report 13665).
Diamond drilling, performed at the same time at four sites along an approximately 150-metre south-north strike length, yielded intercepts of 15.50 and 3.48 grams per tonne gold each over 0.99 metre in hole H-1-84; 1.87 grams per tonne gold over 11.0 metres, including 4.72 grams per tonne gold over 1.1 metres in hole H-3-84; 7.55 grams per tonne gold over 7.2 metres, including 39.20 grams per tonne gold over 1.1 metres in hole H-7-84; 1.83 grams per tonne gold over 4.0 metres in hole H-10-84; 1.53 grams per tonne gold over 5.0 metres in hole H-11-84; 6.55 grams per tonne gold over 1.0 metre in hole H-22-84; 2.64 grams per tonne gold over 5.0 metres in hole H-16-84; 12.5 grams per tonne gold over 2.0 metres in hole H-17-84, 17.60 grams per tonne gold over 1.0 metre in hole H-20-84 and 9.49 grams per tonne gold over 1.0 metre in hole H-21-84 (Assessment Report 13665).
In 1985, diamond drilling (hole 85-24) yielded values up to 310 grams per tonne gold over 2 metres (Property File - Footwall Explorations : Appended report on the Hiller-Churchill Group). Other intercepts include 24.65 grams per tonne gold over 1.0 metre in hole H-8529 and 87.0 grams per tonne gold over 1.0 metre in hole H85-30 (Assessment Report 32531). Also at this time, a rock sample (27055), taken approximately 350 metres to the southeast and at an elevation of 660 metres, assayed 9.97 grams per tonne gold (Property File - Falconbridge Ltd. [1985-11-01]: Geology and DDH Locations - A25-HU Grids - Hiller Claims).
In 1988, sludge samples of drill cuttings from a raise are reported to have averaged 563.6 grams per tonne gold over 2.4 metres (Assessment Report 32531).
In 1989, underground drilling is reported to have yielded up to 21.9 grams per tonne gold over 0.9 metre (Property File - Footwall Explorations Ltd. (1989-01-12): News Clippings - Hiller-Churchill Property).
In 2009, a sample (no. 1) from an exposure on Toray Creek assayed 2.80 grams per tonne gold, whereas another sample (no. 18) from the adit entrance assayed 5.54 grams per tonne gold (Assessment Report 31273).
In 2016, two grab samples (124653 and 124654) from a dump located at the adit portal assayed 349.22 and 244.30 grams per tonne gold with 60.9 and 30.1 grams per tonne silver, respectively (Assessment Report 36472).
The area has been explored in conjunction with the nearby Hiller 8-12 (MINFILE 092L 301) occurrence since the 1960s. In 1980, Esperanza Explorations Ltd. completed a program of rock and soil sampling, prospecting and trenching on the area as the White Dome claim. In early 1984, a program of soil, silt and rock sampling was completed on the area as the Valentine claims. Later that year, Falconbridge Ltd. completed a program of rock sampling, geological mapping, a 4.5 line-kilometre ground magnetic survey, minor trenching and 22 diamond drill holes, totalling 1531.58 metres, on the area as the Hiller 25-26 claims. In 1985, program of soil sampling, airborne geophysical surveys and 10 diamond drill holes, totalling 957 metres, were completed. In 1986, Falconbridge Ltd. completed an airborne geophysical survey on the Hiller and surrounding Zeb claims. Also, at this time the area was prospected as the Whitedome 1 claim.
In 1988, Footwall Explorations Ltd. is reported to have completed an underground development program including 106 metres of drifting, 9.45 metres of subdrifting and 31 metres of raising from an adit located approximately 130 metres to the southeast at an elevation of approximately 480 metres. Also at this time, 900 metres of drilling was completed on the Hiller-Churchill property. The following year, a program of underground drilling was performed.
During 2009 through 2013, A25 Gold Producers Corp. completed programs of rock, silt and soil sampling; prospecting and geological mapping on the area. In 2016, World-Wide Graphite Producers Ltd. prospected and rock sampled the area.