Geographic Minerals



Demesmaekerite is a triclinic-pinacoidal mineral containing copper, hydrogen, lead, oxygen, selenium, and uranium. It is a uranium mineral with the chemical formula: Pb2Cu5(UO2)2(SeO3)6(OH)6•2H2O. It is named to honor Gaston Demesmaeker, a Belgian mining geologist and Director of the Geological Department at the Union Miniere du Haut Katanga.

It can be found alongside other very rare selenium-bearing uranium ores, such as haynesite, guilleminite, marthozite, and piretite.

General Information

  • Category: Oxide mineral
  • Formula: Pb2Cu5(UO2)2(SeO3)6(OH)6•2H2
  • Crystal system: Triclinic
  • Crystal class: Pinacoidal (1) (same H-M symbol)


It is a secondary mineral which contains lead, copper and (the rarer in minerals) selenium, it is a bottle green to brown/yellow color, its crystal habit changes from one form to another form depending on where it is found. It has a Mohs hardness of about 2-3.

  • Cleavage: None
  • Color: Brown, Brownish green, Green, Bottle green.
  • Density: 5.28
  • Habit: Aggregates – Made of numerous individual crystals or clusters.
  • Hardness: 3-4 – Calcite-Fluorite


Demedmaekerite is a rare mineral that occurs in loxidized selenium-bearing copper-cobalt deposits. It can be found at its type locality in the Musonoi mine near Kolwezi in the Katanga Copper Crescent in the Democratic Republic of the Congo, and at Zalesi in Moravia in the Czech Republic. Demesmaekerite is fairly radioactive.

Association: Cuprosklodowskite, kasolite, guilleminite, derriksite, chalcomenite, malachite, selenian digenite.


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