Jankovićite

Properties

Mohs hardness

2

Luster

Metallic

Streak

Black

Density

5.33

Cleavage

Perfect on {100}

Fracture

Uneven

Transparency

Opaque

Crystal system

Triclinic

Diagnostic features

## Identification Identifying jankovićite based on visual characteristics is practically impossible without specialized equipment. Identification requires advanced analytical methods, such as electron microprobe (EDS/WDS) to determine chemical composition and X-ray diffraction (XRD) to confirm crystal structure. Its occurrence as fine, acicular, metallic crystals in a specific geological environment is an indication, but not a basis for identification. ## Distinguishing from Similar Minerals Jankovićite can be confused with many other microcrystalline sulfosalts, such as jamesonite, boulangerite, zinkenite, or other rare thallium sulfosalts (e.g., lorandite, pierrotite). All of them form similar acicular or hair-like crystals with a metallic luster. Definitive differentiation is possible only through chemical analysis, which will show the presence and proportions of thallium, antimony, and arsenic. ## Crystal Forms Jankovićite crystals are very small, reaching up to 1 mm in length. They are acicular or hair-like, elongated, and flexible. They usually occur as tangled, woolly aggregates or radial clusters intergrown with other minerals, most often calcite or realgar.

Geological environment

## Genesis Jankovićite is a low-temperature hydrothermal mineral. It forms in the final stages of crystallization in polymetallic deposits rich in arsenic, antimony, and thallium. In its type locality (Allchar), it is associated with arsenic-antimony-thallium mineralization deposited in volcanic rocks (andesites) and sedimentary rocks (dolomites, tuffs). ## Mineral Associations This mineral co-occurs with other sulfides and sulfosalts. In the Allchar deposit, it has been found in association with realgar, orpiment, lorandite, raguinite, pierrotite, as well as marcasite and pyrite. ## Localities The only confirmed and thoroughly described occurrence of jankovićite in the world is its type locality: the Crven Dol deposit within the Allchar complex, near the town of Kavadarci in North Macedonia. This is the only known locality for this mineral.

Rarity

Extremely rare

For collectors

## Quality Criteria As a "micromount" type mineral, the collector's value of jankovićite depends on the richness of the aggregates and the quality of the crystals visible under a microscope. The most desirable specimens are those with dense, well-formed, undamaged needles, forming distinct aggregates on a contrasting matrix (e.g., on calcite). Association with other rare minerals from this locality, such as lorandite or realgar, is also important. ## Popular Localities The only source of collector specimens is the historic Allchar deposit in North Macedonia. Material from this locality is extremely difficult to acquire and appears on the market very sporadically, usually through specialized rare mineral collectors.

Care and storage

## Cleaning Jankovićite specimens are extremely delicate and rare. Mechanical cleaning is highly inadvisable. If absolutely necessary, compressed air (from a safe distance) can be used to remove dust. Contact with water and any chemicals should be avoided. ## What to Avoid Jankovićite is very soft and brittle, so any touching, rubbing, or impacts should be avoided. As a sulfosalt, it may be sensitive to moisture and atmospheric oxygen, which can lead to its slow oxidation. It should be protected from chemicals, high temperatures, and sudden temperature changes. ## Storage Specimens should be stored under stable conditions, preferably in a closed, padded "micromount" box, to protect them from mechanical damage, dust, and humidity fluctuations. Exposure should be away from direct sunlight and heat sources.

Sources

• IMA Mineral List (CNMNC)