The area is predominantly underlain by massive limestone of the Upper Triassic Quatsino Formation (Vancouver Group) cut by a suite of elongate hornblende-rich dioritic intrusions that commonly contain mafic xenoliths and occupy major fractures. Mafic diorite dykes exhibit varying degrees of endoskarn alteration but exoskarn halos are generally less than 1 metre thick and, in many places, are totally lacking.

The Loyal occurrence area is underlain by limestone of the Quatsino Formation intruded by north trending, skarn-altered mafic dykes more than 250 metres long. Exoskarn halos associated with these dykes seldom exceed 1 metre in thickness. Mafic intrusions outcrop along the northeast coast of Texada Island, below the Loyal mine dump. The intrusions contain rounded to angular mafic xenoliths of coarse hornblendite and gabbro up to 30 centimetres across.

Mineralization within the skarn-altered dykes and adjacent limestone comprise stringers and disseminations of chalcopyrite, bornite, galena, pyrite and sphalerite with associated garnet, epidote, calcite, quartz and variable amounts of magnetite and pyrrhotite. Argentiferous tetrahedrite has also been identified. Locally the skarn contains lenses and alternating bands of sulphides. The zone ranges from 3 to 9 metres width.

The skarn zone has been intermittently exposed along strike by shafts and trenches for 91 metres and is intersected by underground wokings at 91 metres depth. In 1917 and 1918, a total of 342 grams of gold, 4821 grams of silver, and 4668 kilograms of copper were produced from a total of 54 tonnes mined (Mineral Policy data).

Five bulk samples taken in 1963 yielded an average content of 13.1 per cent copper, 3.56 grams per tonne gold, 521.05 grams per tonne silver and 1.1 per cent lead (Assessment Report 2918).