Pirolusita Pseudomorfa parcial tras manganita
Pirolusita is a mineral with formula MnO₂, in the Óxidos group. This specimen comes from Área de Imini, Amerzgane Caïdat, Ouarzazate, Drâa-Tafilalet, Marruecos and joined the Terrium collection in 2025.
Description
Bow-tie-shaped pyrolusite geode replacing manganite. The interior is black, dense and velvety, with very fine microcrystals of matte-silky lustre. The rim shows very bright metallic-grey masses with a strongly fibrous-radial growth.
About Pirolusita
Manganese dioxide (MnO₂) and one of the main ores of this element. At Imini, many specimens sold as «pyrolusite» are in fact manganites, manganese oxyhydroxides with a hydroxyl group (MnO(OH)), partially replaced by pyrolusite. This transformation occurs when manganite oxidises: it loses the hydrogen from the hydroxyl group and progressively turns into pyrolusite, while preserving part of its previous form. That is why the chemical change does not necessarily destroy the original appearance, and can preserve the fibrous/acicular habit while creating that contrast between bright metallic zones and a black, silky, microcrystalline interior.
About the locality
Imini: classic manganese district in the southern High Atlas, more complex than the simple label «Imini Mine». Many collector specimens attributed to Imini do not necessarily come from the main mine, but from nearby workings in the area. The manganese bodies formed in a karst system developed in shallow-marine Cretaceous dolomites, with ores hosted in dolomitic breccias and ferruginous clays. This setting explains the cavities, geodes and replacement textures that make this material so recognisable.
Technical data
- Catalogue No.
- 0122
- Composition
- MnO₂
- Name
- Pirolusita
- Variety
- Pseudomorfa parcial tras manganita
- Group
- Óxidos
- Category
- Cavella
- Associations
- Manganita
- Mine
- Área de Imini
- District / Municipality
- Amerzgane Caïdat
- Province
- Ouarzazate
- Region
- Drâa-Tafilalet
- Country
- Marruecos
- Size (cm)
- 7.5 x 5 x 4.5
- Weight
- 160 g
- Acquired
- 2025
- Etymology
- From the Greek "pyros" (fire) and "lysis" (to dissolve), after its historical use in the reduction of iron oxides in smelting processes.
- Quality
- Notable
- Value trend
- Estable
Related specimens
- Acantita (Paramórfica tras Argentita) — Marruecos
- Anatasa — Pakistan
- Andradita (Melanita) — Marruecos
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- Arfvedsonita — Marruecos
- Armalcolita — España
- Azurita — Marruecos