Middendorfite
Middendorfite is an IMA-recognized mineral species in the silicate class, with the chemical formula K₃Na₂Mn₅Si₁₂(O,OH)₃₆·2H₂O.
It crystallizes in the monoclinic crystal system.
Key properties: Mohs hardness 3–3.5; specific gravity 2.6; Yellowish streak; Vitreous luster; optically biaxial.
IMA symbol Mdd, IMA status: approved, named in 2005.
A late hydrothermal mineral in a hyperperalkaline pegmatite.
It is found associated with Microcline, sodalite, cancrisilite, aegirine, calcite, natrolite, fluorite, narsarsukite, labuntsovite-Mn, mangan-neptunite, donnayite.
The mineral was named to honor Aleksandr Fedorovich von Middendorf (1815–1894), Academician of the Imperial Russian Academy of Sciences.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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