The Bay mine is 1.5 kilometres east of Greenwood, at an elevation of 1021 metres. Access to the mine is from a short side road that joins the main road to Phoenix, 0.4 kilometre to the northwest of the Bay claim.
The area is underlain by part of the Jurassic to Cretaceous Greenwood granodiorite pluton, later referred to as the Cretaceous Anstey pluton, and fine-grained dark-coloured Tertiary dikes. The granodiorite is a mesocratic, medium-grained rock with shearing and some propylitic alteration adjacent to the mineral-bearing fractures. The intrusive is surrounded by a package of chert, siliceous argillite and siliclastic rocks of the Devonian to Permian Knob Hill Group and undivided sedimentary rocks of the Carboniferous to Permian Attwood Group. To the south, ultramafic rocks of the Carboniferous to Permian Mount Roberts Formation outcrop.
The deposit comprises a single quartz vein dipping 35 to 50 degrees east. The vein varies in width from several centimetres to a metre and can be traced for a strike length of 150 metres in the surface workings. North of the shafts, the vein is well delineated. Elsewhere it consists of braided quartz veinlets enveloping lenses of mineralized country rock. Pyrite, galena, sphalerite, chalcopyrite, petzite and free gold comprise the ore minerals in the quartz-carbonate gangue. Finely crystalline petzite with well-defined cubic cleavage has been mistaken for galena in the Bay vein, but may be distinguished by its lighter colour, finer grain and common association with free gold. Pyrite and an occasional small flake of free gold are found in the altered granodiorite adjacent to the vein fissures. High-grade oreshoots are characterized by minutely fractured vitreous quartz with a greenish blue cast, the presence of finely crystalline petzite and the absence of coarsely crystalline galena and sphalerite.
The main ore production has come from the south shaft. This was sunk to a depth of 20 metres following, at first, the hangingwall and then footwall of the vein. In an attempt to locate a faulted segment of the vein, a raise was driven to surface from a 12-metre long tunnel connected on the east to the bottom of the shaft. The north shaft was sunk to a depth of 30 metres and yielded only a small amount of high-grade ore. An important southeasterly dipping fault, located between the shafts, cuts and displaces the vein.
Other faults cut the vein but do not displace it more than a metre. Broken fragments of vein material in the breccia zones and free gold in fault gouge indicate that there has been some post mineral movement along most of the cross faults. Shearing parallel with or at an acute angle to the walls of the vein, and along thin septa of altered country rock in the vein, fractured the quartz along closely spaced parallel planes before the close of mineralization. These fracture planes served as channelways for later mineralizing solutions and are now occupied in some places by thin seams of metallic minerals, chlorite and carbonate, giving the vein a distinctive banded appearance known as ribbon structure.
In 1963, a high-grade galena sample from the dump assayed 0.20 per cent copper, 1.75 per cent zinc, 7.30 per cent lead, 342.0 grams per tonne silver and 45.0 grams per tonne gold (Property File - G. Addis [1963-07-12]: Letters and Reports on the Bay Fraction and Adjoining Claims).
Production from this claim during the period 1904 to 1941 totals 17 kilograms of gold and 14 kilograms of silver from 447 tonnes of mined ore. More than half of the mining was completed in 1935. Exploration continued on the property until 1946.
The area has been explored since the late 1800s with production starting in 1904. In 1908, the Bay and Mavis (MINFILE 082ESE247) claims were combined as the Tiptop claim and operated by Tiptop Mining Co. through 1920. Underground development consists of three inclined shafts and approximately 60 metres of drifting, mostly on the two levels from the southern shaft. Evidence of the intensity of surface exploration in past years is indicated by the numerous trenches.
In 1940 and 1963, the area was examined and sampled by The Granby Mining Co. Ltd.
During 2008 through 2012, Grizzly Discoveries Inc. completed programs of soil, stream sediment and rock sampling, geological mapping and ground geophysical surveys on the area as the Overlander area of the Greenwood property. In 2011, a sample (11SSP049) from the area assayed 7.11 grams per tonne gold and 4.6 grams per tonne silver (Dufresne, M. (2013-11-25): Technical Report for the Greenwood Gold Project).
