The Little Joe (or Coronation) vein, later known as the 77 Vein, was found in the footwall of the 51 Vein (or Ida May/Empire vein - 092JNE002). The 77 Vein is hosted mainly in diorite of the Permian Bralorne Igneous Complex; it trends east from a serpentinite (President Ultramafics, correlative with the Permian and older Shulaps Ultramafics) belt/fault on its northwest end then is sharply deflected southeast along the border of a sodic granite intrusion that is related to the Bralorne complex or the Cretaceous to Tertiary Bendor pluton. The vein extends into the contact zone between the granite and Upper Triassic Pioneer Formation, Cadwallader Group greenstone where it gradually peters out. The vein is richest and widest where it is steepest and where it approaches the sodic granite body, ie. on its eastward trend.

The north dipping vein averages 1.1 metres in width and is well ribboned. It contains quartz, calcite, sericite, ankerite, mariposite and "patchy" scheelite. Sulphide minerals include arsenopyrite, pyrite, minor sphalerite, pyrrhotite, chalcopyrite and occasional stibnite, galena and molybdenite. Gold is closely associated with arsenopyrite. The vein has a vertical continuity of 1500 metres. At lower levels, it averages 38.4 grams per tonne across 2 metres width for 160 metres; the probable (geological) reserve is 80,723 tonnes (Property File - Campbell, 1973). The 77 Vein was the most prolific of the Bralorne veins and produced 1,904,700 tonnes of ore up until the mine closed in 1971.

The 53 Vein, the faulted extension of the 77 Vein, is described as wide and strong and gradually steepens as it approaches the serpentine belt. Both the 77 and 53 veins contain numerous branches in the foot and hanging walls. For detailed geology setting around the Bralorne mine refer to 092JNE001.