Oxyplumboroméite

Chemical formula: Pb₂+₂Sb₅+₂O₇

Oxyplumboroméite is a rare lead-antimony oxide from the roméite group, forming small, octahedral crystals with a resinous luster.

## Characteristics Oxyplumboroméite is a mineral from the roméite group, belonging to the pyrochlore supergroup. Chemically, it is a lead-antimony oxide. It most often forms very small, but well-developed, sharp crystals in the form of octahedra, less frequently cubes or combinations thereof. Crystals usually do not exceed 1-2 mm in size. It occurs as single crystals or small groups grown on the host rock. ## Physical Properties This mineral is characterized by a hardness of about 5 on the Mohs scale and a significant density, ranging from 6.45 to 6.63 g/cm³, which is typical for lead-bearing minerals. It has a resinous to submetallic luster. It is brittle, and its fracture is uneven to conchoidal. It does not exhibit cleavage. ## Colors and Varieties Oxyplumboroméite ranges in color from yellow, through yellowish-brown, brown, reddish-brown, to almost black. Its streak is pale yellow to yellowish-brown. No named varieties are distinguished. ## History and Name The mineral's name refers to its chemical composition – the dominance of oxygen (Oxy) and lead (plumbo) – and its association with stibiconite, which was historically part of the roméite group. It was formally recognized as a distinct mineral species by the International Mineralogical Association (IMA) in 2012 as part of the redefinition of the pyrochlore supergroup. ## Uses Due to its rarity and small crystal size, oxyplumboroméite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals or mineralogical systematics.

Properties

Mohs hardness: 5
Luster: Resinous to submetallic
Streak: Light yellow to yellowish brown
Density: 6.45-6.63
Cleavage: None
Fracture: Uneven to conchoidal
Transparency: Translucent to opaque
Crystal system: Cubic

Diagnostic features

## Identification Key diagnostic features include crystal habit (perfect octahedra), high density (the specimen feels heavy for its size), resinous luster, and color (shades of yellow and brown). It occurs in a characteristic geological environment – the oxidation zones of ore deposits. ## Distinguishing from Similar Minerals It can be confused with other minerals from the pyrochlore supergroup, such as bindheimite or stibiconite. Differentiation often requires advanced chemical analysis (EDS). It differs from sphalerite by its higher hardness and crystal habit. It differs from garnets (e.g., spessartine) by its significantly higher density and lighter streak. ## Crystal Forms It most commonly forms isometric, sharp crystals with an octahedral habit {111}. Less common are cubic {100} or rhombic dodecahedral {110} forms, as well as their combinations.

Geological environment

## Genesis Oxyplumboroméite is a secondary mineral, formed in the oxidation zones (so-called iron caps) of hydrothermal polymetallic deposits rich in lead and antimony. It forms as a result of the weathering of primary sulfides and sulfosalts containing these elements. ## Mineral Associations It co-occurs with other secondary minerals of the oxidation zone, such as cerussite, anglesite, bindheimite, stibiconite, as well as quartz, goethite, and hematite. ## Localities The most important and classic localities for this mineral are the Binchen mine in the Binn Valley (Binntal) in Switzerland and the Clara mine in the Black Forest in Germany. It is also known from small occurrences in the Harz Mountains (Germany) and from the Mounana mine in Gabon.

Rarity

Rare

For collectors

## Quality Criteria Specimens with sharp, well-formed, and lustrous crystals of intense yellow or reddish-brown color are most valued by collectors. Good contrast with the rock matrix and absence of damage are important. Due to the small size of the crystals, rich crystal groups are highly prized. Specimens from classic, historical localities, such as Binntal, are particularly sought after. ## Popular Localities The best quality specimens, considered the world standard for this mineral, come from the Clara mine in Germany and the Binn Valley in Switzerland. Most of the material available on the collector's market originates from these locations.

Care and storage

## Cleaning Specimens should be cleaned very carefully, preferably using compressed air to remove dust. If wet cleaning is necessary, it is recommended to use a soft brush and distilled water, followed by thorough drying. Ultrasonic cleaners should be avoided, as they can damage small crystals. ## What to Avoid Avoid contact with acids and other aggressive chemicals. The mineral is brittle, so it must be protected from impacts and scratches. It does not require special protection from light or humidity, but stable conditions are always recommended. ## Storage It is recommended to store specimens in sealed "micromount" boxes, which protect small and delicate crystals from dust and mechanical damage. A label with precise locality information is crucial for collector value.

Sources

IMA Mineral List (CNMNC)