Demesmaekerite , Chalcomenite Locality: Musonoi Mine, Kolwezi , Western area, Katanga Copper Crescent, Katanga (Shaba) , Democratic Republic of Congo (Zaïre) ( Locality at mindat.org ) Size: 4.3 x 2.3 x 2.5 cm. Here is a good specimen of the rare uranium selenite Demesmaekerite associated with blue Chalcomenite crystals. Musonoi is the type locality for Demesmaekerite (there are only 2 localities known). Chalcomenite is the rare copper selenite and is known from less than 30 localities worldwide, few in good crystals. Demesmaekerite is usually associated with the other uranium selenites and not often with Chalcomenite. These specimens where found during the removal of the uranium dump in the early 1990’s. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Demesmaekerite
A rare lead-copper uranyl selenite named for Belgian mineralogist Gaston Demesmaeker of Katanga's Musonoi mine.
Intro adapted from Wikipedia (CC BY-SA).
Demesmaekerite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Pb₂Cu₅(UO₂)₂(Se⁴⁺O₃)₆(OH)₆·2H₂O.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: Mohs hardness 3–4; specific gravity 5.28; optically biaxial.
IMA symbol Dmm, IMA status: approved, named in 1965.
Rare in the lower oxidized portions of a selenium-bearing Cu–Co deposit.
It is found associated with Cuprosklodowskite, kasolite, guilleminite, derriksite, chalcomenite, malachite, selenian digenite.
The mineral was named to honor Gaston Demesmaeker (1911–), Belgian mining geologist, Director, Geological Department, Union Minière du Haut Katanga.