The Aphebian Rove Formation, located within the Southern Province of the Canadian Shield, is transected by a steeply dipping northeast trending fracture zone named the "Mainland Belt" by Oja (1966). Within this belt are the Rabbit Mountain Group of silver mines, the Beaver Junior mine being a member, situated about 30 miles ESE of Thunder Bay, Ontario. A detailed mapping, structural, and sampling project was undertaken within the vicinity of a 40 foot vertical section of diabase cap rock over argillic shale, and a 50 foot adit driven along strike of the Big Harry Vein, one of the two veins which constitute this mine. The Big Harry vein was found to be a ten inch wide, calcite-quartz vein emplaced in a steeply dipping ENE striking fault with an apparent vertical displacement of ten feet. Its attitude is correlatable with joint maxima in the host rock. Joint maxima is also correlatable with that at Rabbit Mountain and Pigeon Point, Minnesota. The mode of deposition is fracture-filling as indicated by textural evidence. The ore minerals exhibit complex primary and replacement texturals. Mineralization includes native silver, acanthite, allemontite (?), sphalerite, galena chalcopyrite and alteration minerals including smithsonite, cerussite, and covellite. Gangue minerals are calcite, quartz, fluorite, and plagioclase. Vertical and lateral zonation, and a paragenetic sequence are evident.