The Croesus (Lot 866) claim is located on the lower slopes of Mount Attwood, approximately 2.5 kilometres south of Greenwood. Access to the area is from Highway 3 via the Lind Valley road and an old logging road that skirts the northwest spur of Mount Attwood.

The area is bisected by a major southeast-trending fault, along which undivided sedimentary units of the Carboniferous to Permian Attwood Group and ultramafic rocks (serpentinite) of the Carboniferous to Permian Mount Roberts Formation(?) to the northeast are thrust over Permian to Carboniferous Knob Hill Group rocks, consisting of chert, siliceous argillite and siliclastic rocks, to the southwest. To the north these have been intruded by granodioritic rocks of the Cretaceous Anstey pluton.

Locally, a zone of sulphide lenses, 0.3 to 4.5 metres wide, is associated with limestone, greenstone and black argillite formations of the Carboniferous to Permian Attwood Group. The zones have been followed intermittently along strike to the north-northwest for approximately 600 metres from the Croesus (L.866) to Johannesberg (L.2072) Crown grants. A cross section of the main mineralized zone shows 3 metres of limestone and 7.5 metres of massive sulphides and calc-silicates intruded by a 15-metre dike. The principal sulphide minerals are massive pyrite, pyrrhotite and sphalerite with fine-grained chalcopyrite associated with garnet.

To the southeast, on the Fab 4 claim, a 1- to 1.5-metre wide, southeast-trending and vertical-dipping, oxidized quartz vein with minor galena, pyrite and trace chalcopyrite is reported to be exposed for greater than 200 metres along strike.

In 1968, a chip sample assayed 6.9 grams per tonne silver and 1.61 per cent copper (Assessment Report 1648).

In 1983, a chip sample (ASH 83-6) of massive sulphides from the lower Croesus workings yielded 0.45 per cent copper and 6.8 grams per tonne silver over 1.0 metre, whereas another chip sample (ASH 83-9) of massive sulphides from the upper workings yielded 0.38 per cent copper over 2.8 metres (Property File - Ashnola Mining Co. Ltd. [1983-04-15]: Report on the Croesus, Johannesberg, Tanglefoot and Eholt Reverted Crown Grands; And Fab 1 to 6 Two-Post Located Claims).

In 1990, samples of massive pyrrhotite-pyrite-chalcopyrite from the Croesus trench and adit yielded 3.0 and 7.8 grams per tonne silver with 0.387 and 0.714 per cent copper, whereas a sample of southeastern quartz vein yielded 2.4 grams per tonne silver, 0.05 per cent copper and 0.09 per cent lead (Property File - Bombini, S. [1990-07-01]: Property report: Croesus-Johannesburg).

In 1997, diamond drilling yielded up to 1.5 grams per tonne gold over 1.5 metres (Assessment Report 25422).

Early workings on the Croesus claim consist of a 30-metre inclined shaft. The claim was Crown granted to J.E. McEwen in 1902. In 1968 and 1969, Ortega Minerals Ltd. conducted geophysical and geochemical surveys. In 1983, Ashnola Mining Co. Ltd. examined the area. In 1990, the area was prospected and sampled by S. Bombini. In 1996 and 1997, Echo Bay Mines Ltd. completed programs of geological mapping and rock sampling, and drilled six holes, totalling 556 metres. Drill results suggest mineralization at Croesus is associated with intrusion-related silicification, rather than a syngenetic horizon.