The ore bodies of the Hollinger Mine occur in an area of complexly folded and highly altered lava flows intruded by quartz-feldspar porphyry. The ore bodies consist of quartz veins and associated pyritized wall-rock.The investigation is concerned with the paragenesis of the minerals of the ore bodies, particularly the relationship of gold to quartz. Results are given of a microscopic study of thin and polished sections of vein material and wall-rock, supplemented by underground study of the ore bodies.Most of the gold occurs in a quartz-ankerite-pyrite type of ore body and was introduced later than the major period of quartz mineralization. In the veins, gold appears to be genetically related to a pale green sericite and was localized around and in inclusions of such minerals as pyrite, scheelite, arsenopyrite and ankerite. In the wall-rocks, gold is associated with pyrite but is believed to be later than it. A quartz-calcite mineralization was later than most of the gold.Data accumulated during the investigation indicate that the veins were formed predominantly by the filling of fractures successively reopened to the waves of mineralization.