Serpentinites near the head of Ama Creek contain a zone of "whiterock" rodingite alteration in which two irregular veinlike bands of nephrite occur. The serpentine is a tectonic inclusion in albitized gabbro. The area is underlain by rock of the Mississippian to Jurassic Bridge River Complex (Group). A report on the Crest claims, which appear to cover the same ground, describes a 1-metre wide zone of bleached serpentine along the contact of a diorite dyke. The nephrite from the description of the "veins" is apparently not of commercial grade.