Jade has been quarried on Brett Creek, 1.25 kilometres up from its confluence with Marshall Creek, 23 kilometres east of Gold Bridge, B.C.
In the Marshall Creek area, cherts, argillites and minor limestone beds of the Mississippian to Middle Jurassic Bridge River Complex trend east and are intruded by the Permian and older Shulaps Ultramafic Complex, consisting mainly of serpentinized peridotite altered to talc or chloritic schist. Sill-like dacite bodies related to the Tertiary Rexmount Porphyry also intrude the sediments.
At the Greenbay deposit, a large tectonic inclusion of chert lies adjacent to a mass of serpentinite. Metasomatic alteration along the margins of the inclusion has resulted in the development of rodingite, an alteration assemblage of hydrogarnet, clinozoisite and talc. The rodingite contains prominent small masses of thulite (pink zoisite). In places, lenses or vein-like selvages of nephrite occur either within the serpentinite body or along the rodingite-serpent- inite contact. Four lenses, up to 15 metres long by 3 metres wide, contain 9 cubic feet per ton nephrite. The quality of the jade is claimed to improve with depth.
Greenbay Mining is reported to have quarried this deposit in the early 1970's (Geological Survey of Canada Paper 72-53, page 44), with an estimated 590 tonnes of nephrite extracted and sold by 1975. The Brett Creek jade deposit is documented as the Greenbay and the 4-Ton occurrences, approximately 500 metres east of the Greenbay quarry.
In 2012, Gray Rock Resources Ltd. conducted a geological and geochemical assessment of their Silver Stream property, including nephrite and listwanite occurrences (Assessment Report 33490). The Greenbay jade prospect was mapped and sampled by Gray Rock in 2016 and trenched in 2017 (Assessment Report 37320).