The rocks hosting the Monteith occurrence are west striking, dacitic to andesitic fragmental flows of the Lower Jurassic Bonanza Group, 3 kilometres south of a Early to Middle Jurassic Island Plutonic Suite granodiorite batholith. Quartz-diorite porphyry and andesitic dykes intrude the volcanics, with pronounced quartz- sericite, quartz-alunite or quartz-pyrophyllite alteration along the contact zones. The pyrophyllite ore is compact and dense, and ranges from cream, white, pink or light grey to bluish grey when pyrite is present. Minor limonite imparts a yellow to reddish brown stain on weathered surfaces. In thin section pyrophyllite flakes are about 0.01 millimetre in diameter and are readily crushed to a fine smooth powder.

On the Monteith occurrence, the ore contains 42 per cent pyrophyllite and 50 per cent quartz. A chemical analysis returned 81.94 per cent silica, 15.29 per cent aluminum, 0.11 per cent ferric oxide, 0.40 per cent soda, 0.50 per cent potash and 2.40 per cent H2O greater than 105 degrees Celcius (CANMET Report 803, pages 53-135).

Small shipments of pyrophyllite and alunite have been made from the area. Pyrophyllite was mined from a 2 by 2 by 4.5 metre adit at the head of Easy Inlet. Several hundred tonnes of quartz-phyllite were extracted between 1910 and 1914. The ore was mixed with shale and used as a refractory for sewer pipe and fire proofing material. It was also used as polishing powder, soap and cleanser. Several hundred tonnes of ore were also produced in 1937 (Open File 1988-19, page 7).

A report on samples taken from a stockpile in Victoria stated that "it burns steel-hard at Cone 1 and shows good refractiveness" and "is unsuited to replace foliated talc" (Geological Survey of Canada Memoir 24, page 148). The deposit was examined during World War II as a possible source of paper filler, and testing determined it to be a "highly satisfactory ingredient" of whiteware batches for both slip-cast and clay process tiles, electrical insulators and tableware (Minister of Mines Annual Report 1947, page 223).

In 1913, Clapp estimated 90,000 tonnes of pyrophyllite ore were contained in the 0.4 hectares on the Monteith claim (Geological Survey of Canada Summary Report 1913, page 123).

Drilling in 1983 encountered mostly brecciated volcanics with strongly silicified zones of alunite and pyrophyllite with varying proportions of quartz and abundant pyrite (Assessment Report 11374).

See also Morris (092L 072), Sockeye (092L 246), Sic (092L 276) and Monteith Bay (092L 343).