The Dewey occurrences are located on the south slope of Jubilee Mountain, about 3 kilometres southeast of Ymir. The property was first explored in 1926.

The area is underlain by granite of the Late to Middle Jurassic Nelson Intrusions and sediments of the Lower Jurassic Ymir Group, comprising argillite, siltstone and limestone.

Northeast trending quartz veins host disseminated pyrite and minor galena and sphalerite. Northeast trending fault zones have been worked in the past but carry only traces of precious metals. Disseminated pyrite, galena and dark sphalerite with occasional chalcopyrite are reported from a 90 to 122 centimetre wide zone of silicified limestone near a granitic contact.

The vein on the Jubilee claim is exposed by 3 open cuts, has been traced for 15 metres and is 0.91 to 2.44 metres wide. The vein strikes 040 degrees and dips 80 degrees north.

In 1949 and 1952, a total of 40 tonnes was produced yielding 156 grams of gold, 4915 grams of silver, 1700 kilograms of lead and 1786 kilograms of zinc.