The Acorn (Fortynine Creek) placer occurrence is located on Fortynine Creek, a west flowing tributary of the Lower Kootenay River.

The area is underlain by basaltic volcanic rocks of the Lower Jurassic Elise Formation (Rossland Group), which have been intruded by dioritic intrusive rocks of the early Jurassic Eagle Creek Plutonic Complex and syenitic to monzonitic intrusive rocks of the Eocene Coryell Plutonic Suite.

It appears that most of the gold is derived from bars or in crevices in the bedrock of the river bed, or from benches along the side of the creek. No production records have been reported.

The area has been explored for placer gold since at least 1867 with hydraulic workings and a number of shafts and trenches dating to the 1890‘s. In 1942, a shaft was sunk in the creek bed to a depth of 35 metres on the Acorn group and encouraging amounts of gold and scheelite were recovered in a sluice operation.