Triangular shaped actinolite-bearing ultramafic pod in felsic gneiss. As a result of metasomatic infiltration of silica into the ultramafic lenses from the surrounding gneiss, the ultramafic lenses are zoned from rim to core, with decreasing silica content towards the core. This chemical gradation is reflected in mineralogical zoning within the lenses:
RIM phlogopite(phl) + actinolite(act) >>> actinolite(act) >>> actinolite(act) + talc(tlc) >>> talc(tlc) CORE.
Wenatchee Ridge, near Lake Wenatchee, Chelan County, Washington, USA
Photographed in 2003