Ferroefremovite

Chemical formula: (N<sup>3-</sup>H<sub>4</sub>)<sub>2</sub>Fe<sup>2+</sup><sub>2</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>3</sub>

Ferroefremovite is a very rare iron and ammonium sulfate, occurring as tiny, hexagonal crystals in volcanic fumarole environments.

## Characteristics Ferroefremovite is a member of the langbeinite group, forming very small, hexagonal crystals, typically less than 0.1 mm in size. These crystals are tabular or pyramidal and are most often colorless to pale green. Due to its extreme rarity and microscopic size, it is a mineral almost exclusively of scientific interest. ## Physical Properties The crystals exhibit a vitreous luster. Hardness and density have not been precisely measured due to the small size of the samples. ## Colors and Varieties The mineral is usually colorless, sometimes taking on a pale green hue. No varieties are distinguished. ## History and Name Ferroefremovite was first described in 2017 by S.N. Britvin and his team. The name refers to its chemical composition – it is the iron-bearing (ferro) analogue of efremovite, which in turn was named after Ivan Antonovich Efremov, a Russian paleontologist and writer. ## Uses Ferroefremovite has no commercial or industrial applications. Its significance is purely scientific and for specialized micromount mineral collectors.

Properties

Luster
Vitreous
Transparency
Transparent
Crystal system
Trigonal

Diagnostic features

## Identification Identification of ferroefremovite is impossible without advanced laboratory techniques, such as X-ray diffraction (XRD) or energy-dispersive spectroscopy (EDS). In collector conditions, identification relies on a label from a trusted source and verification of the locality (volcanic fumaroles). ## Distinguishing from Similar Minerals It can be confused with other sulfates formed in fumaroles, such as efremovite, boussingaultite, or mohrite. Differentiation based on visual characteristics is impossible and requires chemical analysis to determine the dominant cation (in this case, iron). ## Crystal Forms It forms microscopic, hexagonal crystals with a tabular or pyramidal habit, often clustered in small aggregates.

Geological environment

## Genesis Ferroefremovite forms as a result of volcanic fumarole activity, where hot gases rich in sulfur and other compounds react with volcanic rocks at high temperatures. It crystallizes directly from the gas phase on rock surfaces. ## Mineral Associations It coexists with other fumarolic minerals, such as efremovite, mohrite, hematite, anhydrite, and various halides. ## Localities The only confirmed occurrence (type locality) is the Arsenievskaya fumarole on Tolbachik volcano on the Kamchatka Peninsula in Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a specimen depends on the size and development of the microscopic crystals, as well as their quantity on the rock matrix. The most desirable specimens are those with clearly visible, well-formed crystals under the microscope, contrasting with the substrate. ## Popular Localities The only source of specimens is Tolbachik volcano in Kamchatka, which makes them extremely difficult to acquire and valuable for collectors specializing in micromount minerals and those from type localities.

Care and storage

## Cleaning Due to the microscopic size and fragility of the crystals, any form of mechanical or chemical cleaning is highly inadvisable and may lead to the destruction of the specimen. Specimens should be left in their natural state. ## What to Avoid Contact with water and chemicals that could dissolve or damage the delicate crystals should be avoided. Vibrations, shocks, and changes in temperature and humidity should also be avoided. ## Storage Micromount specimens should be stored in stable, tightly sealed boxes, protected from dust, moisture, and mechanical damage. Display is only possible under a microscope.

Sources

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