Romanechite from the Marquette County, Michigan, USA. Picture taken at the "National Museum of Natural History, Washington D.C, USA. — Photo: Sanjay Acharya · CC BY-SA 3.0
Romanèchite
Also known as: Psilomelane.
The principal mineral in 'psilomelane' — a barium-bearing manganese oxide of supergene manganese deposits.
Intro adapted from Wikipedia (CC BY-SA).
Romanèchite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula (Ba,H₂O)₂(Mn⁴⁺,Mn³⁺)₅O₁₀.
It crystallizes in the monoclinic crystal system (space group C2/m).
Key properties: Mohs hardness 5–6; specific gravity 4.7–4.74; typically gray or black; Black, brownish black streak; Submetallic; dull when massive luster.
IMA symbol Rmn, IMA status: approved, named in 1900.
A product of weathering of manganese-bearing oxides, carbonates, silicates; in sedimentary deposits; as replacement deposits in limestones and dolostones.
It is found associated with Pyrolusite, hausmannite, chalcophanite, braunite, goethite, calcite, quartz.
The name refers to the occurrence at Romanèche, France.
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