Secondary mineral in the oxidized portions of rare-earth-bearing lead deposits.
Approved IMA 1985
Originally found on a museum specimen labelled as coming from Shinkolobwe; however the associated minerals indicate the specimen is more likely from the Kasompi mine, both in Katanga P
Link to MinDat.org Location Data.
Named for Marcel Gysin (1891-1974), Professor of Mineralogy, University of Geneva, Geneva, Switzerland.