Plumboferrite

Chemical formula: Pb₂+[Fe₃+₁₀.₆₇Mn₂+₀.₃₃Pb₂+]O₁₈.₃₃

Plumboferrite is a rare lead and iron oxide, forming characteristic tabular crystals with a metallic luster and black color.

## Characteristics Plumboferrite is a complex oxide of lead, iron, and manganese, belonging to the magnetite-spinel group. Its name refers to its chemical composition – lead (Latin: *plumbum*) and iron (Latin: *ferrum*). It forms well-developed, hexagonal, tabular or platy crystals, often arranged in rosette-like aggregates. Crystal surfaces can be dull or covered with a tarnish, but on a fresh fracture, the mineral exhibits a strong, metallic luster. ## Physical Properties Plumboferrite is a relatively hard mineral, reaching about 4 on the Mohs scale. It is brittle, and its fracture is uneven. It is characterized by a very high density, approximately 6.1 g/cm³, which is a direct result of its high lead content. It also exhibits weak magnetic properties. ## Colors and Varieties This mineral is opaque and has a uniform, black or steel-gray color. The streak, which is the color of the powdered mineral, is characteristic – reddish-brown to black. No color or commercial varieties are distinguished. ## History and Name Plumboferrite was first described in 1881 by Swedish mineralogists Lars Johan Igelström and G. Flink. The name, given by Igelström, comes from the Latin words *plumbum* (lead) and *ferrum* (iron), directly referring to its main chemical components. The type locality (locus typicus) was identified as the Jakobsberg mine in the Filipstad area, Sweden. ## Uses Plumboferrite has no industrial significance. Its occurrence is too rare for it to be an ore of lead or iron. It is exclusively an object of interest for collectors specializing in rare minerals or the systematics of minerals from the spinel group.

Properties

Mohs hardness: 4
Luster: Metallic
Streak: Red-brown to Black
Density: 6.1
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Hexagonal

Diagnostic features

## Identification Plumboferrite can be identified by its characteristic appearance – black, tabular crystals with a hexagonal outline and a strong, metallic luster on a fresh fracture. Key diagnostic features also include very high density, a reddish-brown streak, and weak magnetism. ## Distinguishing from Similar Minerals Plumboferrite is sometimes confused with hematite, magnetite, or ilmenite. - **Hematite** forms similar tabular crystals but has an intensely red streak and is usually not magnetic. - **Magnetite** is strongly magnetic and has a black streak; it also crystallizes in the isometric system, forming octahedra or rhombic dodecahedra, not hexagonal tablets. - **Ilmenite** has a similar appearance and a black streak, but is significantly lighter (lower density) and crystallizes in the trigonal system. ## Crystal Forms Plumboferrite crystals are typically thin to thick tabular, with a distinctly hexagonal outline. They often form aggregates resembling rosettes or fans. They also occur as granular aggregates and masses embedded in rock.

Geological environment

## Genesis Plumboferrite is a metamorphic mineral. It forms as a result of contact metamorphism of iron and manganese ore deposits that have been altered by intruding igneous rocks. It occurs in skarns and metamorphosed Fe-Mn deposits. ## Mineral Associations This mineral often co-occurs with other minerals typical of this environment, such as magnetite, hematite, hausmannite, tephroite, calcite, baryte, native lead, and other rare lead and manganese minerals. ## Localities The most important and historical occurrences of plumboferrite are found in Sweden, in the Långban and Jakobsberg (type locality) areas in Värmland. It is also known from the Kombat mine in Namibia and the Franklin deposit in New Jersey, USA. These are classic localities for many rare minerals.

Rarity

Rare

For collectors

## Quality Criteria The most prized specimens by collectors are those with sharply terminated, well-formed, lustrous crystals with a distinct hexagonal outline. Large sizes of individual crystals (exceeding 1 cm) and their arrangement into aesthetic rosettes or groups enhance their attractiveness. A contrasting matrix, such as white calcite, also significantly impacts the visual value of the specimen. Minimal mechanical damage is also important. ## Popular Localities Classic and most desirable specimens come from the Swedish mines in Långban and Jakobsberg. Material from these historic localities is considered exemplary for this species. Specimens from the Kombat mine in Namibia are also valued in the collector's market.

Care and storage

## Cleaning Plumboferrite specimens should be cleaned very carefully, using a soft brush to remove dust. For heavier soiling, a damp cloth or a soft-bristled brush moistened with distilled water can be used. Ultrasonic cleaners should be avoided, as they can damage brittle crystals. ## What to Avoid The mineral is sensitive to acids, which can etch and damage the crystal surface. Contact with household and laboratory chemicals should be avoided. Prolonged exposure to moisture can lead to the formation of secondary tarnishes. ## Storage Plumboferrite specimens are best stored in stable conditions, in closed boxes or display cases, to protect them from dust and mechanical damage. Due to its lead content, it is recommended to wash hands after handling the mineral.

Sources

IMA Mineral List (CNMNC)