Balićžunićite

Chemical formula: Bi<sup>3+</sup><sub>2</sub>O(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>

Balićžunićite is an extremely rare bismuth sulfate, forming microscopic, platy crystals with a pearly luster.

## Characteristics Balićžunićite is a bismuth oxysulfate, occurring as extremely small, colorless, platy crystals that rarely exceed 0.2 mm in length. These crystals form fan-shaped or radial aggregates. Due to their size, visual features are difficult to observe without specialized equipment, such as a scanning electron microscope (SEM). ## Physical properties The crystals exhibit a pearly luster on cleavage surfaces and a vitreous luster on other faces. They are transparent to translucent. Hardness and density have not been precisely measured due to the small size and rarity of the material; however, the density calculated from the formula and unit cell parameters is 6.45 g/cm³. ## Colors and varieties The mineral is colorless. No varieties have been distinguished. ## History and name Balićžunićite was discovered in the Schmiedestollen mine, in the Wittichen area of the Black Forest (Baden-Württemberg, Germany). It was approved as a new mineral species by the International Mineralogical Association (IMA) in 2009 (IMA2009-050). The name honors Professor Tonči Balić-Žunić (born 1952), a crystallographer from the University of Copenhagen, for his contributions to mineral crystal chemistry. ## Uses Balićžunićite has no industrial application. Its significance is purely scientific and as a collector's item, being an extremely rare mineral.

Properties

Luster
Pearly
Streak
White
Density
6.45
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of balićžunićite is practically only possible using advanced laboratory methods, such as X-ray diffraction (XRD) and chemical spectroscopy (EDS/WDS). Visually, in the field or in a collection, it is impossible to distinguish from many other secondary sulfates without specialized equipment. Characteristic, though difficult to observe, are microscopic, platy crystals in radial aggregates. ## Differentiation from similar minerals It can be confused with other secondary bismuth sulfates, such as pucherite or schumacherite, with which it often co-occurs. Certain differentiation requires chemical and crystallographic analysis. ## Crystal forms It forms very small, thin, platy crystals with a rhombic or lath-like outline, elongated along the [100] axis and flattened parallel to {010}. These crystals combine into fan-shaped, radial, or irregular aggregates.

Geological environment

## Genesis Balićžunićite is a secondary mineral, forming in the oxidation (weathering) zones of ore deposits containing bismuth. At its type locality (Schmiedestollen mine), it formed as a result of the weathering of native bismuth in the presence of sulfides, which supplied sulfate ions. It forms in vugs and fissures in quartz rock. ## Mineral associations This mineral co-occurs with native bismuth, bismutite, pucherite, schumacherite, namibite, beyerite, atelestite, and quartz. ## Localities The only confirmed and described locality for balićžunićite in the world is its place of discovery: Schmiedestollen mine, Wittichen, Schenkenzell, Black Forest, Germany.

Rarity

Extremely rare

For collectors

## Quality criteria As a "micromount" type mineral, the quality of a specimen is primarily determined by the abundance and good development of microscopic crystals within the field of view. Specimens with distinct, sharp, radial aggregates of balićžunićite are most valued, ideally in association with other rare bismuth minerals. Contrast with the surrounding rock (matrix) also enhances aesthetic value. ## Popular localities The only source of specimens is the type locality in Germany. Material from this location is extremely limited and highly sought after by collectors specializing in rare minerals and "micromount" specimens.

Care and storage

## Cleaning Due to the extreme delicacy and small size of the crystals, mechanical cleaning is not recommended and can lead to the destruction of the specimen. Any cleaning attempts should only be undertaken by specialists under a microscope. ## What to avoid Avoid contact with chemicals, ultrasound, vibrations, and sudden temperature changes. The mineral is brittle and susceptible to mechanical damage. ## Storage Balićžunićite specimens should be stored exclusively in specialized, padded "micromount" boxes, protected from dust, shocks, and moisture. Avoid direct exposure to sunlight.

Sources

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