Zincoberaunite

Chemical formula: Zn²⁺Fe³⁺₅(PO₄)₄(OH)₅·₆H₂O

Zincobéraunite is a rare, hydrated zinc and iron phosphate, forming aggregates of small, acicular crystals with a reddish-brown color.

## Characteristics Zincobéraunite is a mineral from the phosphate group, a zinc analogue of béraunite. It occurs as radial or tangled aggregates, as well as crusts and rosette-like clusters. It forms very small, acicular or bladed crystals, rarely exceeding 1-2 mm in length, which makes individual crystals difficult to observe with the naked eye. It is most often observed as felt-like or woolly masses growing on the host rock. ## Physical Properties Zincobéraunite crystals exhibit a silky or vitreous luster. This mineral is translucent. Due to the small size and fragility of the crystals, determining its hardness and density is difficult; these values have not been precisely established. ## Colors and Varieties Zincobéraunite is characterized by a reddish-brown to brown color, sometimes with an orange tint. Its streak is a lighter, yellowish-brown. There are no distinct color varieties or commercial varieties of this mineral. ## History and Name The mineral's name, approved in 2014, refers to its chemical composition – the presence of zinc (Latin: *zincum*) – and its structural similarity to béraunite. It was discovered and described based on material from the "Rotläufchen" mine in Waldgirmes, Germany, which is its type locality. ## Uses Zincobéraunite has no industrial applications. It is solely an object of interest for collectors specializing in rare phosphate minerals and minerals from specific localities (so-called "systematics").

Properties

Mohs hardness: 3
Color: Pale olive green to black
Luster: Vitreous
Streak: Yellow-brown
Density: 2.92
Cleavage: Good on {100}
Fracture: Splintery
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Zincobéraunite is identified by its characteristic appearance – radial or felt-like aggregates of small, acicular crystals with a reddish-brown color. The environment of occurrence, i.e., the oxidation zones of deposits rich in phosphates and zinc, is also crucial. ## Distinguishing from Similar Minerals It can be confused with other minerals from the béraunite group, especially béraunite itself, from which it is practically impossible to distinguish without advanced chemical analyses (e.g., EDS). Cacoxenite, strengite, or rockbridgeite may also have a similar appearance, but they differ in the form of aggregates and often in color hue. Certain identification requires specialized equipment. ## Crystal Forms This mineral forms elongated, acicular or bladed crystals, which almost always occur in radial, spherical, or irregular, tangled aggregates. Rosette-like forms and crusts are less common.

Geological environment

## Genesis Zincobéraunite is a secondary phosphate mineral, forming in the oxidation (weathering) zones of ore deposits, in an environment rich in phosphorus, iron, and zinc. It forms in voids and fissures of sedimentary rocks, such as greywackes or shales, which have undergone hydrothermal processes. ## Mineral Associations It most often co-occurs with other secondary phosphates, such as strengite, rockbridgeite, dufrénite, as well as with quartz, goethite, and hematite. In its type locality, it is also associated with béraunite. ## Localities The most important and best-documented occurrence of zincobéraunite is its type locality – the "Rotläufchen" mine in Waldgirmes, Hesse, Germany. This is a historic iron ore mine, known for the occurrence of rare phosphate minerals. In addition, individual finds have been reported in Spain (the "La Paloma" mine, Murcia).

Rarity

Very rare

For collectors

## Quality Criteria The most prized specimens by collectors are those with well-formed, radial aggregates of intense, reddish-brown color, contrasting with the light host rock. Due to the microscopic size of the crystals, the aesthetics of the entire aggregate and the absence of damage are crucial. Specimens from the type locality ("Rotläufchen") are particularly sought after. ## Popular Localities The only commercially significant and historically important locality, from which almost all specimens in collections originate, is the "Rotläufchen" mine in Germany.

Care and storage

## Cleaning Zincobéraunite specimens are extremely delicate. They should be cleaned only very carefully, using compressed air to remove dust. Any contact with water or a brush can irreversibly damage the tiny, acicular crystals. ## What to Avoid Avoid contact with water and all chemicals. The crystals are brittle and sensitive to shocks and ultrasound. Specimens should not be exposed to direct sunlight, which can cause fading. ## Storage It is recommended to store specimens in closed, padded boxes (micromount type) to protect them from dust, mechanical damage, and humidity changes. Display should be in stable conditions, away from sources of vibration.