Khrenovite

Chemical formula: Na<sub>3</sub>Fe<sup>3+</sup><sub>2</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>3</sub>

Chrenovite is a rare sodium iron arsenate, forming tiny, prismatic crystals of an intensely brown color.

## Characteristics Chrenovite is an arsenate mineral characterized by its occurrence in the form of very small, prismatic crystals. It typically forms acicular or hair-like aggregates, with individual crystals rarely exceeding 0.2 mm in length and 10-20 micrometers in thickness. Its color is intensely brown to reddish-brown, which, combined with a silky or vitreous luster, gives it a distinctive appearance. ## Physical Properties This mineral is transparent to translucent. Due to the extremely small size of its crystals, many of its physical properties, such as hardness or density, have not been precisely measured and are only calculated values. It exhibits strong pleochroism in shades from yellowish-brown to reddish-brown. ## Colors and Varieties Chrenovite occurs in a uniform range of colors from brown to reddish-brown. No varieties have been distinguished. ## History and Name The mineral was named in honor of Evgeny Chrenov (1949–2021), a Russian volcanologist from the Institute of Volcanology and Seismology in Petropavlovsk-Kamchatsky. It was approved as a new mineral species by the IMA in 2018 (IMA2018-056). The type locality is the Arsenievskaya fumarole on Tolbachik volcano in Kamchatka, Russia. ## Uses Chrenovite has no industrial application. Its significance is purely scientific and collectible, as a unique and rare mineral from a very specific volcanic environment.

Properties

Luster
Vitreous
Streak
Light brown
Density
4.26
Cleavage
None
Fracture
Brittle
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of chrenovite is only possible using advanced laboratory methods, such as X-ray diffraction (XRD) or electron microprobe chemical analysis (EDS/WDS). In the field or in a collection, it is visually indistinguishable due to its size and resemblance to other alluaudite-group minerals. ## Distinguishing from Similar Minerals It can be confused with other small, brown arsenates found in volcanic fumaroles, such as johillerite, dmitryivanovite, or other alluaudite-group minerals. Definitive distinction requires specialized analysis of chemical composition and crystal structure. ## Crystal Forms Chrenovite forms elongated, prismatic crystals, often acicular or hair-like. They occur as porous, tangled aggregates or as crusts on other minerals.

Geological environment

## Genesis Chrenovite is a volcanic mineral, formed by sublimation from volcanic gases in high-temperature fumaroles. It crystallizes in an oxygen-, arsenic-, and sodium-rich environment, at temperatures ranging from 450-600°C. ## Mineral Associations This mineral coexists with other rare arsenates and sulfates formed under similar conditions, such as anhydrite, hematite, tenorite, aphthitalite, johillerite, dmitryivanovite, ericlaxmanite, powellite, sylvite, and halite. ## Localities The only confirmed locality for chrenovite in the world is its type locality – the Arsenievskaya fumarole, located on the second cinder cone of the Northern Breakthrough of the Great Fissure Eruption of Tolbachik volcano in Kamchatka, Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria Since chrenovite is a "micromount" type mineral, its collectible value depends on the richness and aesthetics of the aggregates on the host rock. The most prized specimens are those with clearly visible, well-formed, though still microscopic, crystals forming dense clusters. The presence of rare associated minerals is also important. ## Popular Localities The only source of collectible specimens is the type locality on Tolbachik volcano in Kamchatka.

Care and storage

## Cleaning Chrenovite specimens are extremely delicate and small. No mechanical or chemical cleaning is recommended. They should be left undisturbed on the host rock. ## What to Avoid Avoid contact with water, chemicals, ultrasound, and any vibrations or impacts. Sudden temperature changes can damage delicate crystals or the host rock. ## Storage Specimens should only be stored in specialized, sealed "micromount" boxes that protect against dust, moisture, and mechanical damage. Observation is only possible under a microscope.

Sources

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