Krivovichevite

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

Krivovichevite is a rare secondary sulfate mineral, forming colorless, tabular crystals with a hexagonal outline.

## Characteristics Krivovichevite is a hydrated lead and aluminum sulfate. It occurs as small, colorless, hexagonal, tabular crystals, usually not exceeding 0.3 mm. The crystals are transparent and exhibit a vitreous luster. They often form aggregates or thin coatings on other minerals. ## Physical Properties The mineral is characterized by a hardness of approximately 2.5 on the Mohs scale. It is brittle, and its density, calculated based on the chemical formula and unit cell parameters, is 5.75 g/cm³. It exhibits perfect cleavage in one direction. ## History and Name Krivovichevite was discovered in the Kombat Mine in Namibia. Its name honors Professor Sergey Vladimirovich Krivovichev (born 1972), a Russian crystallographer and mineralogist from St. Petersburg State University, for his contributions to the crystal chemistry of oxysalt minerals. ## Uses Due to its rarity and microscopic size, krivovichevite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and micromounts.

Properties

Mohs hardness
2.5
Luster
Vitreous
Streak
White
Density
5.75
Cleavage
Perfect on {0001}
Fracture
Uneven
Transparency
Transparent
Crystal system
Trigonal

Diagnostic features

## Identification Identification of krivovichevite is based on its characteristic crystal form – small, colorless, hexagonal tablets. Vitreous luster and co-occurrence with other secondary lead minerals in oxidation zones are also important clues. Final confirmation requires advanced analytical methods such as X-ray diffraction (XRD) or chemical analysis (EDS). ## Distinguishing from Similar Minerals It can be confused with other colorless, tabular sulfates or carbonates, such as cerussite or anglesite, which often occur in the same environment. Krivovichevite is distinguished from them by its hexagonal crystal form and specific chemical composition, containing both lead and aluminum. ## Crystal Forms It forms thin, tabular crystals with a hexagonal outline. These crystals often occur as rosette-like or irregular clusters and aggregates.

Geological environment

## Genesis Krivovichevite is a secondary mineral, formed in the oxidation zones of polymetallic ore deposits rich in lead. It forms as a result of reactions between sulfate-rich solutions and primary minerals containing lead and aluminum under conditions of low temperature and pressure. ## Mineral Associations At the type locality (Kombat Mine), it co-occurs with quartz, calcite, hematite, anglesite, cerussite, linarite, chenite, leadhillite, and susannite. ## Localities The only confirmed locality of krivovichevite in the world is its type locality – the Kombat Mine, in the Grootfontein district of Namibia.

Rarity

Very rare

For collectors

## Quality Criteria The quality of krivovichevite specimens is assessed based on the size and development of the crystals, their transparency, and the aesthetics of the entire aggregate. Most valued are specimens with well-formed, sharp hexagonal crystals, forming visually attractive groups on a contrasting matrix. Due to the microscopic nature of the mineral, the quality of the specimen under magnification is crucial. ## Popular Localities The only source of krivovichevite specimens is the Kombat Mine in Namibia, which makes it extremely important for collectors of this mineral.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using compressed air to remove dust. Due to the small size and fragility of the crystals, contact with water or brushes is not recommended. ## What to Avoid Avoid contact with all chemicals, especially acids, which can easily damage the mineral. It is sensitive to mechanical damage, so shocks and abrasion should be avoided. It should not be heated or subjected to ultrasonic cleaning. ## Storage Krivovichevite specimens, typically in the form of micromounts, should be stored in stable conditions, in closed boxes protecting them from dust and mechanical damage. Exposure to moisture should be avoided.

Sources

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