The Rioanda 15-16 occurrence is located on the south facing slope of a hill between George Creek and the Loughborough Inlet, approximately 1.8 kilometres south-southeast of George Lake.

The area is underlain by a persistent band, greater than 12 kilometres long, of stratified metavolcanic and metasedimentary rocks of the Upper Triassic Quatsino and Karmutsen formations (Vancouver Group). The band trends northwest and separates Jurassic to Cretaceous Coast Plutonic Complex rock of two different compositions, diorite and granodiorite.

Locally, a north-northeast trending zone of fracture filling and replacement sulphide mineralization occurs near a quartz diorite contact with meta-sediments and meta-volcanic pendant rocks. The mineralization consists of sphalerite, chalcopyrite and molybdenite associated with variable amounts of pyrrhotite, magnetite and pyrite. Two chip samples (15619 and 15618) across the mineralized zone assayed 0.95 and 2.42 per cent copper and 1.0 and 1.95 per cent zinc with 17.1 and 18.8 grams per tonne silver over 3.0 metres and 1.35 metres, respectively (Property File - William M. Sharp [1969-01-20]: Report - Rioanda Cu-Zn-Mo Prospect, Loughborough Inlet).

The area was originally prospected and staked in 1964 as the Rioanda claims. Over the next two years, minor programs of prospecting, geological mapping, geochemical sampling and a preliminary magnetometer survey were completed.