The Jo 85 occurrence is located 4.5 kilometres south of the most southwestern edge of Humphrey Lake at approximately 1400 metres in elevation on a southwest slope of the westernmost extent of the Mount Tom Range.

The occurrence area is underlain by mudstone, siltstone, shale and fine clastic sedimentary rocks of the Lower Permian to Upper Jurassic Cache Creek Complex.

The mineralization was noted to contain significant values of silver, and anomalous values of gold from quartz-rich porphyrite with pyrite and very fine spinel.

In 1983, Golden Porphyrite Ltd. completed a sampling program to the south of Humphrey Lake near the occurrence. Anomalous silver values from sediment and soil sampling were noted.

In 1985, Golden Porphyrite Ltd. completed a sampling program to the south of Humphrey Lake. Reported results included the rock chip sample RM0052 grading 20.0 grams per tonne silver and 0.12 grams per tonne gold, and heavy sediment samples grading 2.64 grams per tonne gold on JO 83, and 4.4 grams per tonne gold and 8.0 grams per tonne silver on JO 80. In conclusion, sediment sampling results indicated a northeast-southwest–trending mineralized zone (Assessment Report 13888).