Small serpentine-magnesite bodies that occur in precambrian rocks. They have been quarried for magnesite and serpentine.
Note on the mineral list: so-called "martite" from here is actually hematite (Raade, 1982).
References:- Jøsang, Ottar (1966): Geologiske og petrologiske undersøkelser i Modumfeltet. Norges Geologiske Undersøkelse nr 235, 91-97
- Raade, G. (1970): Dypingite, a new hydrous bascic carbonate of magnesium, from Norway. American Mineralogist 55, 1457-1465
- Raade, G. (1982): Die sogenannten "Martite" von Snarum (Norwegen"). Aufschluss 33: 405-407
- Eldjarn, K. (1988): Etter Neumann". NAGS-nytt 15 (1-4), 62 (in norwegian) [on a find of pyroaurite ?]
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http://www.nags.net/Nags/english/articles_werner/magnesite_modum.htm 43 entries listed. 31 valid minerals. 3 type localities (valid minerals).