In 2019-2020, pods of extremely fine-grained, pure monomineralic nephrite jade were found in situ in central Wyoming, USA. Here referred to as type 1 nephrite, this jade occurs as 'olive' green open-space fillings of mineralogically pure tremolite that are hosted by shear zones and fractures within broad zones of massive quartz-clinozoisite/epidote alteration that overprint Archean-age gneisses. This unusual geological setting is characterised by the absence of associated serpentinite or dolomite that typically are seen in other known jade belts worldwide. The main occurrence described here, named the Sky Zone, is associated with a >400-m-long nephritebearing zone consisting mostly of coarse-grained, metasomatically altered and recrystallised mafic/ultramafic units hosted by mafic and quartzofeldspathic gneisses. Jade from these metasomatic units--here referred to as type 2 nephrite--consists of mottled dark green, mineralogically impure, medium-grained material. The physical and chemical properties of both nephrite types are consistent with those published in the literature for nephrite jade. Mineralogical, textural and chemical evidence indicates that the fine-grained type 1 nephrite formed through direct precipitation of tremolite from hydrothermal fluids within fractures extending outwards from a well-defined shear zone in close association with felsic intrusive bodies. [ABSTRACT FROM AUTHOR]