Dark orange crystals of the extremely rare mineral milanriederite (IMA 2018-041) from the type and only known locality worldwide, the famous Kombat mine in Namibia, close to Tsumeb. — Photo: David Hospital · CC BY-SA 4.0
Milanriederite
Milanriederite is an IMA-recognized mineral species in the silicate class, with the chemical formula (Ca,REE)₁₉Fe³⁺Al₄(Mg,Al,Fe³⁺)₈Si₁₈O₆₈(OH,O)₁₀.
It crystallizes in the tetragonal crystal system (space group P4/nnc). It is a member of the Vesuvianite structural group.
Key properties: Mohs hardness 6; specific gravity 3.53; Vitreous luster; optically uniaxial.
IMA symbol Mlrd, IMA status: approved, named in 2018.
By hydrothermal and metasomatic replacement and fracture-filling of dolostones.
It is found associated with Baryte, calcite, jacobsite, hausmannite, glaucochroite, native copper.
The mineral was named to honor Czech mineralogist Professor Milan Rieder (b. 1940), for his contributions to mineralogy and service to the international mineralogical community.