Zavaritskite

Chemical formula: Bi<sup>₃+</sup>OF

Zavaritskite is a rare bismuth oxyfluoride, most often forming earthy coatings and pseudomorphs after other bismuth minerals.

## Characteristics Zavaritskite is a bismuth oxyfluoride, most commonly occurring as earthy, dusty, or fine-grained aggregates and coatings. Less frequently, it forms pseudomorphs (replacement forms) after primary bismuth or bismuthinite. Well-formed, macroscopic crystals are extremely rare and appear as thin, square tablets. It is usually opaque and has a dull or slightly greasy appearance. ## Physical Properties This mineral is relatively soft, with a Mohs hardness ranging from 2 to 3.5. It is characterized by a very high density, ranging from 7.5 to 7.6 g/cm³, which makes specimens surprisingly heavy for their size. The luster is most often earthy, dull, and less frequently greasy. ## Colors and Varieties Zavaritskite ranges in color from grayish-white and yellowish-gray to gray and brownish. There are no distinct color varieties or commercial names. ## History and Name The mineral was first described in 1962 by E. I. Dolomanova, V. M. Senderova, and M. T. Yanchenko. Its name commemorates Alexander Zavaritsky (1884–1952), a prominent Russian petrologist and member of the USSR Academy of Sciences. ## Applications Zavaritskite has no industrial applications. It is solely an object of scientific and collecting interest.

Properties

Mohs hardness: 2-3.5
Luster: Greasy, Dull, Earthy
Streak: White to grayish white
Density: 7.5-7.6
Cleavage: Perfect on {001}, rarely observed
Fracture: Uneven to Earthy
Transparency: Opaque
Crystal system: Tetragonal

Diagnostic features

## Identification Characteristic features of zavaritskite include its high density, low hardness, earthy appearance, and occurrence as a weathering product of bismuth minerals. It often forms pseudomorphs, retaining the external shape of the primary mineral (e.g., bismuth). ## Distinguishing from Similar Minerals Zavaritskite can be confused with other secondary bismuth minerals. It differs from bismite (Bi₂O₃) by its generally less intense, more grayish or brownish color (bismite can be bright yellow or greenish). It differs from bismutite (Bi₂(CO₃)O₂) by its lack of reaction (effervescence) when in contact with hydrochloric acid. Definitive identification is only possible with laboratory methods, such as X-ray diffraction (XRD). ## Crystal Forms It most commonly occurs as earthy, massive aggregates or as coatings. Crystals, which are extremely rare, take the form of thin, square tablets, often arranged in groups or rosettes.

Geological environment

## Genesis Zavaritskite is a secondary mineral, formed in the oxidation (weathering) zones of hydrothermal deposits and pegmatites rich in bismuth. It forms as a result of alterations of primary minerals, such as native bismuth and bismuthinite, under the influence of fluorine-bearing waters. ## Mineral Associations It most often co-occurs with the minerals from which it forms, namely native bismuth and bismuthinite. It is also accompanied by other secondary bismuth minerals, such as bismite, bismutite, atelestite, as well as quartz and fluorite. ## Localities The most important occurrences of this mineral are in Russia, at its discovery site - Sherlova Gora (Transbaikal Krai). It is also known from the Kara-Oba tungsten deposit in Kazakhstan and the Dzhida deposit in Buryatia (Russia). Occurrences have also been reported in Germany (Saxony) and the USA (California).

Rarity

Rare

For collectors

## Quality Criteria The most highly valued by collectors are specimens with well-preserved pseudomorphs after bismuth or bismuthinite, especially if the primary, unaltered mineral is still visible. Association with other rare bismuth minerals also enhances its appeal. Due to the rarity of well-formed crystals, even microscopic but sharp tablets are sought after. ## Popular Localities The type locality, Sherlova Gora in Russia, is considered classic and provides the best historical material. Specimens from this location, often in the form of pseudomorphs, are the standard for this species.

Care and storage

## Cleaning Zavaritskite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, it can be rinsed with distilled water and then thoroughly dried. Due to its softness, ultrasonic cleaners and strong friction should be avoided. ## What to Avoid The mineral is susceptible to mechanical damage, so it should be protected from scratches and impacts. Contact with strong acids, which can damage it, should be avoided. ## Storage It is recommended to store specimens in separate, padded boxes or display cases to prevent contact with harder minerals. It should be protected from dust and moisture.