The St. Patrick mine is located on Crown grant Lot 15474, in the Slocan Mining Division. The property is at 1035 metres elevation above sea level on the north side of Hamill Creek east of the Duncan River.

Regionally, the area lies within the Kootenay Arc near the margins of the Ancestral North American Terrane. The Kootenay Arc is a curving belt of highly deformed metasedimentary and metavolcanic rocks which includes the Upper Proterozoic Horsethief Creek Group, the Eocambrian Hamill Group, the Lower Cambrian Badshot Formation and the lower Paleozoic Lardeau Group. The volcano-sedimentary sequence is intruded by numerous Ordovician, Devonian and Mississippian granitoid plutons. The rocks have undergone regional metamorphism to middle or upper greenschist facies (Paper 1993-1).

Rocks at the mine are dark to light grey, fine grained mica schist and cream to grey fine-grained limestone. Some of the schist contain narrow lenses of whitish limestone. The micaceous schists are part of the upper Index Formation of the Lardeau Group while the limestone represents the Badshot Formation. The rocks are highly contorted and cut by numerous faults and shear zones. The dominant schistosity strikes northwest and dips very steeply east. Fold axis within the limestone plunge 10 to 15 degrees northwest.

The underground workings are developed on a number of shear zones dipping steeply to the east and striking mainly between north and northwest. The shears consist of 10 to 60 centimetres of crushed and sheared rock, on either side of which the rocks are contorted and dragged. The shear zones transect the dominant foliation at high angles.

Mineralization occurs as scattered lenses along the shears and faults as replacement of limestone. It consists of fine to medium-grained galena and sphalerite in a gangue of fine-grained siderite. Along the faults, the lenses of mineralization are either massive or banded, crustified, and include layers of schist. Locally, massive galena is present. Replacement mineralization exists in four separate shear zones; all have similar character and mineralogy. The best developed shear (F2 shear) transects a layer of limestone near the crest of a fold. The limestone is contorted, but in general has a low dip to the north corresponding to the plunge of the fold. It is somewhat micaceous and is cut by a poorly developed cleavage. Replacement of the limestone by fine-grained siderite and medium-grained sphalerite and galena has taken place both along the cleavage and layers within the limestone (Bulletin 49).

The shear is mineralized over a width of as much as 1 metre and a length of 15 metres. It has been exposed in several small adits, trenches and shafts. Between 1919 and 1938, 38 tonnes of ore were extracted form the four mineralized shears to produce 38,164 grams of silver, 13,967 kilograms of lead and 6708 kilograms of zinc.