Orange-yellow concretions, formed by superficial alteration processes can be observed on the surface of a very late Precambrian black shale exposed in the Sör-Fron area. X-ray, thermal, and chemical studies on these concretions have shown that they consist of halotrichite. This is the first known occurrence of halotrichite in Norway.
Occurance of Halotrichite at Sør-Fron (Oppland). Contributions to the mineralogy of Norway, no. 38