Magnetoplumbite
Chemical formula: Pb<sup>2+</sup>Fe<sup>3+</sup><sub>12</sub>O<sub>19</sub>
A magnetic lead iron oxide, a rare mineral with strong magnetic properties and hexagonal crystals.
Properties
- Mohs hardness
- 6
- Luster
- Metallic
- Streak
- Black
- Density
- 5.51
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Hexagonal
Diagnostic features
## Identification The key diagnostic feature of magnetoplumbite is its strong magnetism – it is one of the few non-metallic minerals that are so strongly attracted by a magnet. Other features include its black color, metallic luster, hexagonal crystal shape, and high density. ## Distinguishing from Similar Minerals Magnetoplumbite can be confused with magnetite (Fe₃O₄). However, it is distinguished by the presence of lead, which results in a significantly higher density. Magnetite crystallizes in the isometric system (usually as octahedra), while magnetoplumbite forms hexagonal, tabular crystals. Definitive differentiation requires chemical analysis. ## Crystal Forms It most commonly forms thin, tabular crystals with a hexagonal outline. These can occur individually or form small clusters and aggregates. More massive or granular forms are less common.
Geological environment
## Genesis Magnetoplumbite is a metamorphic mineral. It forms as a result of contact or regional metamorphism of iron and manganese ore deposits that also contain lead. It forms in an iron- and lead-rich environment under conditions of elevated temperature and pressure. ## Mineral Associations It often co-occurs with other minerals typical of metamorphosed ore deposits, such as hematite, magnetite, hausmannite, franklinite, jacobsite, as well as lead minerals like galena or barite. ## Localities The most important and classic locality for magnetoplumbite is Långban in Värmland, Sweden, where the best-formed crystals originate. It is also known from Franklin, New Jersey (USA), and the Kombat mine in Namibia. Occurrences have also been reported in small quantities in other localities worldwide, including Russia and Australia.
Rarity
Very rare
For collectors
## Quality Criteria Specimens with well-formed, sharp, hexagonal crystals with smooth and lustrous faces are most valued by collectors. The absence of mechanical damage is important. A contrasting association with accompanying minerals, such as white barite, can significantly enhance the specimen's attractiveness. Crystal size is also an important factor, as most specimens are small. ## Popular Localities By far the most sought-after and classic specimens come from the Långban mine in Sweden. They are considered exemplary for this mineral. Specimens from Franklin, USA, are also valued in specialized collections.
Care and storage
## Cleaning Dry cleaning with a soft brush or compressed air is recommended to remove dust. If necessary, a damp cloth can be used, followed by immediate and thorough drying of the specimen. Prolonged contact with water should be avoided. ## What to Avoid Avoid contact with acids and other aggressive chemicals that can damage the mineral's surface. Do not heat the specimen, as this may affect its magnetic properties. ## Storage Store in a dry place under stable conditions. Due to its strong magnetism, specimens should be kept away from sensitive electronic devices, magnetic cards, and other minerals that may be susceptible to magnetic fields. It is best to store it in a separate, padded box.