Plumbogottlobite

Chemical formula: Pb₂+Mg(V₅+O₄)(OH)

A very rare basic lead magnesium vanadate of the adelite-descloizite group, known mainly from its type locality in Thuringia.

## Characteristics Plumbogottlobite is a very rare vanadate mineral belonging to the large adelite-descloizite group. Chemically, it is a basic lead magnesium vanadate. It occurs as transparent crystals that exhibit a characteristic orange-brown color. It is the lead analogue of gottlobite, where lead replaces calcium in the crystal structure. It was described as a distinct mineral species relatively recently, which is associated with advances in the precision of analytical methods used in modern mineralogy. ## Physical properties This mineral is characterized by a Mohs hardness of 4-4.5, meaning it is relatively soft and can be scratched by harder materials. It features a high density of 5.359 g/cm³, which is a direct result of the presence of the heavy element lead in its crystal lattice. The fracture of the mineral is uneven to conchoidal. The streak left on an unglazed porcelain plate is light orange-brown. It crystallizes in the orthorhombic crystal system. ## Colors and varieties Plumbogottlobite occurs in an orange-brown color. Due to the very limited number of known specimens and narrow occurrence, no specific color or morphological varieties of this mineral have been described to date. ## History and name The mineral's name directly refers to its chemical composition and structural relationship. The prefix "plumbo-" indicates the presence of lead (from Latin *plumbum*), while the second part of the name refers to gottlobite. Gottlobite itself was named after the historic Gottlob Hill in Thuringia, which is the type locality of both minerals. The Glücksstern Mine, from which the first described specimens originated, is a historic mining center known for the occurrence of rare secondary minerals.

Properties

Mohs hardness: 4-4.5
Color: orange-brown
Streak: light orange-brown
Density: 5.359
Fracture: Irregular/Uneven,Conchoidal
Transparency: Transparent
Crystal system: Orthorhombic

Diagnostic features

## Identification Visual identification is extremely difficult due to its similarity to other minerals of the adelite-descloizite group. Definitive identification requires advanced analytical studies, such as X-ray diffraction (XRD) or microprobe chemical analysis (EDS/WDS), to confirm the presence of lead, magnesium, and vanadium in the correct proportions. ## Distinction from similar minerals Visually, this mineral can be confused with many other orange-brown vanadates and arsenates, including gottlobite, descloizite, or mottramite. Distinction from the related gottlobite relies solely on demonstrating the dominance of lead over calcium in the crystal structure. ## Crystal forms It crystallizes in the orthorhombic system. It typically forms very fine crystals and microscopic aggregates, often encrusting other minerals in rock cavities.

Geological environment

## Genesis It forms as a secondary mineral in the oxidized zones of ore deposits, in an environment enriched in lead, magnesium, and vanadium. ## Mineral associations It co-occurs with other secondary minerals, often with other members of the adelite-descloizite group as well as manganese and iron oxides typical of weathering zones. ## Localities The mineral is known primarily from its type locality: the historic Glücksstern Mine on Gottlob Hill (Friedrichroda, Gotha District, Thuringia), Germany. It is a mineral with a very restricted occurrence.

Rarity

Extremely rare

For collectors

## Quality criteria Due to its extreme rarity, every confirmed specimen of this mineral has high scientific and systematic value. Specimens are typically microscopic, so evaluation primarily focuses on crystal development under magnification and their transparency. ## Popular localities The only significant source of specimens is the type locality at the Glücksstern Mine in Germany. Specimens from this location end up almost exclusively in specialized systematic collections.

Care and storage

## Cleaning Specimens should be cleaned using only a soft brush and distilled water. Due to the lead and vanadium content, caution should be exercised: avoid inhaling dust and wash hands thoroughly after handling the mineral. ## What to avoid Contact with acids and strong chemicals must be strictly avoided, as they can damage the crystal surfaces. The mineral should be protected from mechanical shocks due to its relatively low hardness and brittleness. ## Storage Store in a dry place, preferably in closed collector boxes (micromount type), which protect against dust, moisture, and accidental mechanical damage.

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External references

https://www.mindat.org/min-499356.html