The Sack occurrence lies astride the faulted boundary between north trending belts of the Upper Triassic Nicola Group. The Quilchena fault is a high angle fault striking 010 to 030 degrees across the central portion of the property, generally parallel to Moore Creek. Lithologies within this 500 metre wide zone consist mainly of quartz-hornblende-feldspar gneiss and biotite-chlorite schist. Foliations follow the regional north trend and dip moderately to the east. West of this fault zone is the Lower Jurassic Nicola batholith, which is granitic to dioritic in composition. East of the Quilchena fault, the property is underlain by Upper Triassic Nicola Group andesite and basalt, minor interbedded pyroclastics and sediments.

Alteration and mineralization appear to be structurally controlled. The north striking regional fault and numerous secondary northwest trending fractures are associated with high level quartz- chalcedony veins, argillite alteration, enhanced arsenic-mercury geochemical values and quartz-carbonate veins in brecciated volcanics. The veins strike approximately 010 degrees and dip 85 degrees west and carry minor amounts of molybdenite, pyrrhotite, pyrite, chalcopyrite and ferrimolybdenite. Molybdenite occurs as 1 to 3 millimetre rosettes and blebs. Skarn pockets also occur.

A recent discovery of quartz-chalcedony breccia zones is restricted to a lahar or agglomerate zone at least 4 metres thick, dipping gently to the west. The zone contains numerous quartz- chalcedony-calcite veins and veinlets. A rock sample from one of these veinlets with a true width of 30 centimetres assayed 3.97 grams per tonne gold (George Cross Newsletter #29, 1988).