The Duke of York prospect is situated on the east bank of the Similkameen River, 12.5 kilometres south of Princeton.

This area on the east side of the Similkameen River is underlain by intrusive rocks of the Lost Horse Intrusions and the Smelter Lake stock (Copper Mountain Intrusions), both of Early Jurassic age, and volcanics of the Upper Triassic Nicola Group. The Nicola Group volcanics were previously included with the Wolf Creek Formation (Geological Survey of Canada Memoir 171). All units are unconformably overlain to the east by volcanics and sediments of the Eocene Princeton Group.

The prospect is hosted mostly in the Lost Horse Intrusions, which are comprised of medium-grained porphyritic diorite, monzonite and syenite. Minor remnants and fault bounded inclusions of altered tuff and andesite of the Nicola Group are also present.

The Lost Horse rocks are intensely altered over an area 460 metres long and 240 metres wide in the northern part of the deposit. The rocks have been totally or almost totally replaced by orthoclase, resulting in a deep pink to brick red, fine to medium-grained rock, devoid of mafic minerals, in which only outlines of the original plagioclase phenocrysts can be seen. A second area of alteration occurs to the south, where Lost Horse rocks have undergone intense albite-epidote alteration. These rocks are pale green to light grey or nearly white and devoid of magnetite. The original plagioclase and pyroxene have been reduced to irregular, ragged patches of albite, plagioclase, sericite and epidote, and chlorite and epidote respectively.

Faulting and fracturing in the northern part of the deposit is moderate to strong, and mostly oriented in a northeasterly and northwesterly direction. To the south, the rocks are cut by the northeast-striking Honeysuckle break, and several subsidiary northeast-striking faults.

Mineralization generally consists of pyrite-chalcopyrite fracture-fillings and disseminations in intrusives and volcanics, preferably in zones of stronger northeast faulting. Copper mineralization occurs in three distinct zones. On the Duke of York Crown-granted claim, mineralization occurs in intrusive rocks in the area of intense orthoclase alteration. A chip sample from a trench in this zone assayed 0.37 per cent copper over 90 metres (Geological Survey of Canada Memoir 171, page 36).

In the second zone, on the Honeysuckle Crown-granted claim (Lot 3263), 200 metres to the south, mineralization is found in intrusives and volcanics along the Honeysuckle break and subsidiary faults. This zone trends northeast for 270 metres and is 100 metres wide. Samples from here have assayed 4.5 per cent copper and 1.4 to 2.7 grams per tonne gold (Minister of Mines Annual Report 1899, page 741).

A third area of mineralization occurs 300 metres northeast of the Duke of York zone. Here, mineralization consists of chalcopyrite and pyrite, with minor chalcocite and covellite, in Lost Horse rocks, near the contact with overlying sandstone and volcanic breccia of the Princeton Group. A sample assayed 1.75 per cent copper (Geological Survey of Canada Memoir 171, page 36). One drill hole averaged 0.6 per cent copper over 6.1 metres (George Cross News Letter No. 218, 1966, hole C4).

The deposit was first prospected in 1898 by the Day Brothers. A number of trenches and an adit, 82 metres long, were excavated some time between 1908 and 1934. Cumont Mines Ltd. drilled six holes and completed 800 metres of trenching in 1966. Some percussion drilling is reported for 1969. The deposit was also trenched and sampled by Similco Mines Ltd. in 1990.