Contributions to the mineralogy of Norway. No. 21. On the occurrence of Mn-poor piemonite and withamite in Norway.

New occurrences of piemontite and withamite are recorded, together with a reconsideration of certain 'piedmontites' described by O. Andersen ( 1911) . Partial chemical analyses and semi-quantitative spectrographic analyses of these minerals are presented together with some optical data. It is concluded that the 'piedmontite' recorded by O. Andersen (1911) from Notodden and material recently found at Tinnsj√ł should be classified as withamite. Material from Furenes is identified as true piemontite. With the exception of one occurrence of withamite, the piemontites and withamites in Norway have unusually low manganese contents.

The piemontites and withamites in Norway appear to have originated either in fairly low-grade regional metamorphic environments or as late crystallization or replacement products associated with pegmatites and quartz veins within rocks which have undergone higher grades of metamorphism. This is in agreement with the observations of previous workers.