Dwornikite

Chemical formula: Ni<sup>2+</sup>S<sup>6+</sup>O<sub>4</sub>·H<sub>2</sub>O

Dwornikite is a rare, hydrated nickel sulfate, most commonly forming greenish, microcrystalline coatings and crusts.

## Characteristics Dwornikite is a mineral from the sulfate group, chemically a hydrated nickel sulfate. It occurs extremely rarely, most often forming very fine, microscopic crystals smaller than 0.1 mm. It is usually observed as earthy or powdery coatings, crusts, and efflorescences on other minerals, especially gersdorffite. Its crystals, visible only under high magnification, are tabular or short prismatic. ## Physical Properties Due to its occurrence in very fine aggregates, determining many physical properties, such as hardness or density, is difficult. The mineral has a vitreous luster and is transparent to translucent. The density calculated based on the chemical formula and unit cell parameters is 3.16 g/cm³. ## Colors and Varieties Dwornikite has a characteristic light green or grayish-green color. No color varieties or commercial varieties are distinguished. ## History and Name The mineral was discovered in the "Podgórze" uranium ore mine in Kowary, Lower Silesia (Poland). It was described and recognized by the International Mineralogical Association (IMA) in 1982. Its name honors Edward J. Dwornik (1919-2003), an American mineralogist and chemist working for the United States Geological Survey (USGS), who first synthesized an artificial analogue of this mineral in 1965. ## Uses Dwornikite has no industrial application. It is solely an object of interest for collectors specializing in rare minerals, systematic mineralogy, and minerals from Poland.

Properties

Mohs hardness
2
Luster
Vitreous
Streak
White
Density
3.16
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identifying dwornikite without specialized equipment is practically impossible. It is identified based on its light green color, occurrence as fine coatings on nickel ores (mainly gersdorffite), and its characteristic geological environment. Final confirmation requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical microanalysis (EDS). ## Distinguishing from Similar Minerals Dwornikite can be confused with other secondary nickel sulfates, such as morenosite (NiSO₄·7H₂O) or retgersite (NiSO₄·6H₂O). Morenosite contains more crystallization water and usually forms acicular crystals. Retgersite has a darker, bluish-green color. It is distinguished from annabergite (nickel arsenate) by its chemical composition (sulfate vs. arsenate) and often a lighter shade of green. ## Crystal Forms Dwornikite crystals are microscopic, with tabular or short prismatic habits. It mainly forms earthy, powdery aggregates, as well as thin crusts and coatings.

Geological environment

## Genesis Dwornikite is a secondary mineral, forming in the oxidation (weathering) zones of ore deposits containing nickel minerals. It forms as a result of slow dehydration of more hydrated nickel sulfates, such as morenosite, under conditions of low air humidity, e.g., in dry mine workings. ## Mineral Associations This mineral most often occurs in association with gersdorffite (the main source of nickel), annabergite, erythrite, morenosite, retgersite, as well as gypsum and epsomite. ## Localities The most important and type locality (localitas typica) of dwornikite is the "Podgórze" mine in Kowary, Lower Silesia, Poland. This is the only confirmed and well-documented locality of this mineral in the world.

Rarity

Very rare

For collectors

## Quality Criteria The quality of a dwornikite specimen is primarily assessed based on the abundance of the coating and its color intensity. The most valued samples are those where the green coating is clearly visible and covers a significant area of the host rock, preferably in association with other rare secondary minerals. Due to the microscopic size of the crystals, their form is not a criterion for visual assessment. ## Popular Localities The only source of collector specimens is the historical type locality – the "Podgórze" mine in Kowary, Poland. Specimens from this location are rare on the market and represent a valuable acquisition for specialized collectors.

Care and storage

## Cleaning Dwornikite specimens are extremely delicate and sensitive. They occur as coatings that can be easily removed. Mechanical cleaning is out of the question. If necessary, the surface can be very carefully rinsed with alcohol, which evaporates quickly, minimizing contact with moisture. ## What to Avoid Contact with water, which can dissolve the mineral, must be absolutely avoided. Dwornikite is sensitive to airborne moisture, so it should not be stored in humid conditions. It should also be protected from all chemicals and temperature fluctuations. ## Storage It is recommended to store specimens in airtight, sealed containers (so-called "perky boxes") away from sources of moisture and direct sunlight. It is best to place a desiccant (silica gel) in the container.

Sources

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