Pirolusita
Pirolusita is a mineral with formula MnO₂, in the Óxidos group. This specimen comes from Cercal, Santarém, Portugal.
Description
Well-defined black acicular crystals on ochre matrix. Cavernous texture, with aggregates scattered in cavities of the matrix.
History of this specimen
Offered to me by Marcos López, one of the major collectors in Spain and a dealer from Ponferrada, during the Salamanca Mineral Fair in May 2025.
About Pirolusita
Acicular pyrolusite commonly grows in the oxidised zones of manganese deposits, forming fibrous aggregates.
About the locality
The Cercal deposit (Portugal) is practically inactive at present, and is known for pyrolusite in acicular aggregates on ferruginous matrix. Well-formed specimens are scarce and usually come from old collections.
Technical data
- Catalogue No.
- 0049
- Composition
- MnO₂
- Name
- Pirolusita
- Group
- Óxidos
- Category
- Asteris Explosio
- District / Municipality
- Cercal
- Province
- Santarém
- Country
- Portugal
- Size (cm)
- 5 x 4 x 2.5
- Weight
- 45 g
- Ex-collection
- Marcos López
- Etymology
- From the Greek 'pyr' ('fire') and 'lousis' ('washing'), in allusion to its historical use in cleaning and smelting processes. Pyrolusite has been one of the principal industrial manganese minerals.
- Quality
- Buena
- Value trend
- Estable
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