The Bull River Iron showing at the summit of Fenwick Mountain, east of the Bull River, is hosted by limestones, shales, sandstones, and dolomites of the Helikian Kitchener Formation (Purcell Supergroup) which have a general north-northwest strike and an easterly dip of 20 to 35 degrees. This stratigraphy is cut on the northeast side of the summit by a northwesterly trending diorite dyke which is up to 15 metres thick.

The iron mineralization has three main modes of occurrence: (1) relatively pure hematite fills short and narrow fractures within and near the margins of the diorite dyke; (2) hematite impregnates and selectively replaces sedimentary beds at the margins of the intrusion and the hematite decreases in abundance away from the intrusive contact; and (3) an impure hematite that is silica-rich, occurs as fine-grained, dark grey-black pods and specks of generally ovoid shape within more siliceous stratigraphy. These first two types have values in the order of 50 to 55 per cent iron, trace phosphorus, 20 to 25 per cent silica and less than 1 per cent sulfur.

The extent of the mineralization is unclear.

In mid-1983 a reconnaissance V.L.F. electromagnetic test survey was flown along northwest-southeast flight lines for R.H. Stanfield (Assessment Report 11681). Diagrams show this survey to have been over the Bull River Iron occurrence. Also, for R.H. Stanfield, in late 1983, an airborne electromagnetic and magnetic survey was conducted over the Steeple claims in 1983 along east-west flight lines (Assessment Report 12575). The survey lines appear to have been just north of the occurrence. In 1999, one diamond drill hole within the Steeples East Group of claims (Steeples #5) was completed to test an oval shaped magnetic low about 3 kilometres north of the Bull River Iron showing.

Refer to Bull River (082GNW002) for details of the greater Bull River property which contained the Bull River Iron showing and a minimum of 25 other documented mineral occurrences as of October 2022.