The area of the Rainbow 3W showing is underlain by a stock of granodioritic quartz feldspar porphyry of the Late Cretaceous Bulkley Plutonic Suite. The stock is known as the Sunsets stock and intrudes basalt to andesite to rhyolite volcanic rocks of the Lower Jurassic Telkwa Formation, Hazelton Group.

In 1990 and 1991, sampling by Skeena Resources was done at an intensely gossaned K-feldspar porphyritic granodiorite contact with andesite. A 50 metre wide gossan is reported to occur in the granodiorite. A rhyolite dike up to 3 metres wide is also observed. Pyrite and traces of chalcopyrite occur in the zone. Of 5 samples from various lithologies, only one grab sample taken across 2 to 3 metres of andesitic rock yielded significant results. Sample YR 19 assayed 0.078 gram per tonne gold, 12.7 grams per tonne silver and 0.23 per cent copper (Assessment Report 21765).

Refer also to King (093L 041) for general information on the El Toro property, a large property that was worked by of Lions Gate Energy Inc from 2007 to present (2015) and encompassed the Sunset Basin area which contains this showing.

Refer to Fly (093L 045) for related details.