The String occurrence lies within the Finlayson Lake Volcanogenic Massive Sulphide District. The Finlayson Lake District comprises an isolated outlier of Yukon-Tanana and Slide Mountain terranes and affiliated overlap assemblages. The district is bounded by the Tintina Fault to the southwest and the Inconnu Thrust Fault to the northeast.

Yukon-Tanana and Slide Mountain terranes represent continental arc and back-arc basin sequences that developed along the ancient Pacific margin of North America during late Devonian and through Permian (Piercey et al., 2001). Pericratonic rocks of Yukon-Tanana Terrane and oceanic rocks of Slide Mountain Terrane are juxtaposed against rocks of the North American continental margin sequence along the post-Late Triassic Inconnu Thrust Fault (Murphy et al., 2006). Yukon-Tanana and Slide Mountain terranes in the Finlayson Lake District are characterized by variably deformed and metamorphosed, lower greenschist to amphibolite facies metasedimentary and metavolcanic rocks and affiliated metaplutonic suites. 

Prior to the Late Triassic, the Yukon-Tanana Terrane experienced regional shortening and uplift. This terrane was imbricated with mid-Paleozoic Slide Mountain Terrane after the Late Triassic and the resultant structural stack was subsequently thrust onto the North American continental margin before the Mid-Cretaceous (Murphy et al., 2006). 

During the Mesozoic era two types of intrusion were emplaced in the Finlayson Lake District. The first includes several unmetamorphosed Early Jurassic mafic and intermediate composition plutons. The second consists of Late Cretaceous two-mica quartz monzonite and granite. 

The String occurrence is underlain by Devonian, Mississippian and older(?) Nasina Assemblage and Carboniferous to Permian Anvil Group. Thick quaternary cover is mapped to the northwest of the property.

Drilling by Westmin in 1997 identified the primary lithology as fine-grained clastic sediments hosting pyrite. Graphitic argillites and siltstones with interbedded units of pale green mafic tuff were intersected by both holes. Pyrite was seen throughout the core as disseminations and coarse-grained aggregates and is commonly associated with quartz veining.

A sample collected during the 2011 trenching program by Archer, Cathro & Associates (1981) Ltd returned coincident elevated values for gold (2,570 ppb), arsenic (2,650 ppm), antimony (>1%), copper (3.51%) and zinc (5,510 ppm) in the centre of the property. This sample was from a small boulder of finely to coarsely crystalline vuggy quartz with abundant tetrahedrite, malachite and azurite.