The Shenango (Rainbow) occurrence is located in Shenango Canyon, along the southern side of the Salmo River and approximately 700 metres southeast of Rosebud Creek.

Regionally, the area is underlain by quartzites, pelites, phyllites, limestone and argillites of the Cambrian Laib Formation and quartz arenite sedimentary rocks of the Neoproterozoic to Lower Cambrian Hamill Group, which have been intruded by granodioritic rocks of the Cretaceous Anstey pluton to the northeast.

Locally, the Lower Cambrian Laib Formation limestones (Reeves Member) and micaceous quartzites are exposed with what are likely Active Formation black, graphitic argillites on the north and south side of the Salmo River at Shenango Canyon. The geology described is similar to that in the vicinity of the Lone Silver (MINFILE 082FSW019) occurrence to the east; the Shenango occurrence is along the west strike extension of the Black Bluff fault. Highly sheared, graphitic argillite is exposed in an adit south of the Salmo River.

Mineralization is of two types:

(1) An adit (collapsed) exposes a sulphide-bearing quartz vein, which averages 15 centimetres in width, strikes northeast and dips shallowly to the southeast. The vein contains a white quartz gangue with small lenses of galena, sphalerite and pyrite. The vein is hosted by sheared and faulted graphitic phyllites/slates.

(2) A gossanous zone, 3 to 20 metres wide, of Reeves Member limestone and/or dolomitized marble contains at least five separate, 20- to 70-centimetre wide, stratabound zones of layer-parallel, banded sulphides composed of disseminated pyrite with minor galena, sphalerite and magnetite. The zone is restricted to the south side of the northerly band of limestone and the sulphides are traceable along 125 metres of strike length on the north and south sides of the Salmo River and east and west of the adit exposing the mineralized vein.

Another gossanous shear zone hosting zinc (sphalerite) mineralization is reported to the east, near Rosebud Creek.

A sample across 76 centimetres contained 44.56 grams per tonne silver, 1.06 per cent lead, and 2.5 per cent zinc (Bulletin 41, page 149). Analysis indicates less than 1 per cent combined lead and zinc and less than 30 grams per tonne silver within the disseminated zone (Bulletin 41, page 149).

Drilling of an unknown age intercepted 0.6 metre yielding 1.4 per cent lead and 0.3 per cent zinc in hole DD-151 (Property File - Cochenour Willans Gold Mines (unknown): Rainbow Canyon Drill Hole Sections).

In 1959, a high-grade sample of dump material from an adit is reported to have yielded 307.8 grams per tonne silver, 10.0 per cent lead and 6.2 per cent zinc (Assessment Report 25655).

In 1997, a 0.60-metre chip sample (R97-3-7) from a gossanous zinc-rich and iron-poor zone (type 2 mineralization), located east of the adit, assayed 19.8 grams per tonne silver, 3.472 per cent zinc, 0.173 per cent lead and 0.099 per cent cadmium, whereas a high-grade dump sample (R97-3-1) assayed 48.0 grams per tonne silver, 18.85 per cent zinc and 0.260 per cent cadmium (Assessment Report 25655).

In 1998, trench samples from a newly exposed (type 2 mineralization) zone, located east of the adit, yielded 20.7 grams per tonne silver, 4.530 per cent zinc and 0.164 per cent lead over 1.90 metres (sample CJR98-101); 7.9 grams per tonne silver, 2.500 per cent zinc and 0.349 per cent lead over 3.2 metres (Sample CJR98-102) and 2906 grams per tonne silver, 8.391 per cent zinc, 0.518 per cent lead with 0.129 per cent cadmium over 5.0 metres (Sample Bow-1; Assessment Report 25655). Sampling (1701 and 1702) of the former trench No. 3, located west of the adit, yielded 0.842 per cent zinc and 0.292 per cent lead over 4.4 metres from the west wall and 0.521 per cent zinc with 0.255 per cent lead over 4.5 metres from the east wall of the trench (Assessment Report 25655).

In 1929 and 1930, the Consolidated Mining and Smelting Co. completed four drillholes, totalling 373.8 metres, and six opencuts on the Rainbow occurrence. Other workings reported at this time include two adits, one each on the south and west [north?] sides of the river.

During 1951 through 1956, Diem Mines Ltd. completed programs of ground geophysical surveys and three percussion drill holes to the northeast on the Grouse claims. Also, in 1951 MacDonald Mines Ltd. optioned the Rainbow claims and completed three drillholes, totalling 780.0 metres. In 1960, McIntyre Porcupine Mines Ltd. completed a program of soil sampling and a ground electromagnetic survey on the area as the A 1-4 claims.

In 1984, M. Fox completed a program of prospecting and a ground electromagnetic survey on the area as the Huron 1-8 claims. In 1997 and 1998, Cominco Ltd. completed a program of rock and soil sampling, geological mapping and 10.5 line-kilometres of ground magnetic and electromagnetic surveys on the area as the Bow 1-37 claims. In 1999, Redhawk Resources Inc. soil sampled the area.

In 2018, S.K. Smith and B.T. Lorenzen soil sampled the area as the Pend Oreille Zinc property.