Droninoite

Chemical formula: Ni₂+₃Fe₃+(OH)₈Cl·₂H₂O

Droninoite is an extremely rare secondary mineral of the hydrotalcite group, found in iron meteorites as a product of their weathering.

## Characteristics Droninoite is a hydrated nickel and iron hydroxychloride, belonging to the hydrotalcite supergroup. It occurs as very fine-grained, earthy or waxy aggregates, forming coatings, crusts, and fillings in small fissures. Its crystals, in the form of microscopic hexagonal plates, are extremely rarely observed. It typically forms aggregates with a pale, greenish color. ## Physical Properties This mineral is very soft, with a Mohs hardness of approximately 1.5-2. It exhibits a waxy, dull, or earthy luster. It is translucent to opaque. Its density, calculated based on the chemical formula and unit cell parameters, is approximately 2.96 g/cm³, but it is not measurable in typical aggregates. ## Colors and Varieties Droninoite ranges in color from pale green and yellowish-green to bluish-green. No distinct color varieties or commercial varieties are recognized. ## History and Name The mineral's name comes from its discovery locality – the Dronino meteorite, found in 2000 in the Ryazan Oblast, Russia. It was described and recognized as a new mineral by the International Mineralogical Association (IMA) in 2006, and its full description was published in 2007. It is a typical mineral for the weathering processes of iron meteorites under terrestrial conditions. ## Applications Droninoite has no industrial applications. It is solely an object of scientific and collecting interest, especially for those specializing in meteorite minerals.

Properties

Mohs hardness: 1.5-2
Luster: Waxy to earthy
Streak: Pale greenish white
Density: 2.96
Cleavage: Perfect on {0001}
Fracture: Uneven
Transparency: Translucent to opaque
Crystal system: Trigonal

Diagnostic features

## Identification The key diagnostic feature of droninoite is its origin – it occurs exclusively as a product of the weathering of iron meteorites. It can be recognized by its light green color, very low hardness, and waxy or earthy appearance. Co-occurrence with metallic iron and nickel (kamacite, taenite) is a strong indicator. ## Distinguishing from Similar Minerals Droninoite can be confused with other secondary nickel minerals, such as reevesite or honessite, which also form green coatings. Final and certain differentiation requires advanced analytical methods, such as X-ray diffraction (XRD) or electron microprobe chemical analysis, which will show the presence of chlorine in the droninoite structure. ## Crystal Forms It forms microcrystalline aggregates, coatings, and crusts. Individual crystals are in the form of hexagonal plates, but they are usually too small to be seen without high magnification.

Geological environment

## Genesis Droninoite is a secondary mineral. It forms as a result of the weathering of iron meteorites (atakites) under terrestrial conditions. It forms when primary iron-nickel alloys (kamacite and taenite) react with oxygen and water rich in chloride ions. ## Mineral Associations This mineral occurs in direct proximity to the meteoritic minerals from which it forms: kamacite and taenite. It is also accompanied by other weathering products, such as goethite, akaganéite, and native nickel. ## Localities The type locality is the Dronino meteorite found in Russia. Its presence has also been confirmed in several other iron meteorites that have undergone weathering processes on Earth.

Rarity

Extremely rare

For collectors

## Quality Criteria The collector's value of droninoite is inextricably linked to the meteorite specimen on which it occurs. The most prized samples are those with rich, well-formed aggregates of the mineral that clearly contrast with the metallic background. The size and quality of the meteorite matrix itself also play a key role in assessing value. ## Popular Localities The most known and valued specimens come from the Dronino meteorite (Russia), which is its type locality. Any new discovery of this mineral in another meteorite is considered significant from a scientific and collecting point of view.

Care and storage

## Cleaning Droninoite specimens are extremely delicate and sensitive. Cleaning should be kept to an absolute minimum. A soft brush or a stream of compressed air can be used to remove loose dust. Any contact with water and chemical agents should be avoided. ## What to Avoid This mineral is sensitive to moisture, which can lead to its chemical degradation. It should be protected from water, acids, detergents, and all other chemicals. Due to its low hardness, it is very susceptible to mechanical damage and abrasion. ## Storage It is recommended to store specimens in stable, dry conditions, preferably in tightly sealed containers (e.g., "membrane boxes" or micromount boxes). Protect from dust and moisture.

Sources

IMA Mineral List (CNMNC)