At the Trilby showing, galena and sphalerite with pyrite are contained in a quartz gangue within a diorite dyke of the Proterozoic Moyie Intrusions intruding quartzites and argillites of the Helikian Aldridge Formation (Purcell Supergroup). A tunnel about 300 metres above the river exposes faulted and broken sediments for approximately 20 metres from the portal, but there is little evidence of mineralization.

Later reports indicate that four adits, up to 50 metres long, expose galena, pyrite and chalcopyrite mineralization as blebs and pods with Moyie diorite dykes that crosscut Aldridge Formation shales and argillites. The east striking, vertically dipping dykes are parallel and host sulphides pods up to 38 centimetres wide.

Field traverses were done over an area of anomalous magnetic susceptibility on these prospects. Grab and composite samples were taken from outcrop subjected to whole rock analysis and petrographic study. Bull River reported that samples of altered diorite from Copper King showed anomalous gold values and elevated Fe2O3, as defined by whole rock analysis, and was the likely cause of the magnetic anomaly. The Trilby traverse also yielded samples with elevated Fe2O3, and petrographic analysis indicated the presence of titanium and iron in rocks adjacent to the Trilby showings (unpublished private report by de Souza (1999) as recorded in Bird and Crowie (2022)).

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