The Holly occurrence is underlain to the east by massive limestone of the Upper Triassic Quatsino Formation in fault contact (Holly fault) with pillow basalt breccias and amygdaloidal basalt of the Upper Triassic Karmutsen Formation, both of the Vancouver Group. Diorite dykes intrude along fracture and fault zones.

Mineralization consists of gold-bearing pyritic quartz and quartz-calcite vein structures which comprise predominantly northwest but also northeast to east striking, steeply dipping complex zones in fractured, brecciated and sheared basalt. Within these structures are generally one main and up to two or three narrower intervals where the basalt is intensely brecciated and quartz-flooded with pyrite, rare native gold and occasionally chalcopyrite. Silver values up to 15.76 grams per tonne have also been reported from drill core assays (Assessment Report 13731).

Trenching has exposed a major vein structure for 90 metres along strike and is 2.5 to 13 metres wide. The main interval of quartz flooding varies from 0.13 to 4.65 metres wide with an average width of 1.2 metres. A secondary vein structure is 50 metres northeast of and subparallel to the main structure and has been exposed for 100 metres along strike. It varies from 0.5 to 7.4 metres wide.

A 453 tonne bulk sample of the southeastern most 21 metres of the major vein structure averaged 1.16 grams per tonne gold over 1.7 metres (Assessment Report 16702).