Middendorfite

Chemical formula: K₃Na₂Mn²⁺₅Si₁₂(O,OH)₃₆·2H₂O

Middendorfite is a very rare, recently discovered silicate mineral, occurring as tiny, brown aggregates.

## Characteristics Middendorfite is a very rare, hydrated potassium, sodium, and manganese silicate, approved as a new mineral species by the International Mineralogical Association (IMA) in 2021. It occurs as very fine, platy or fibrous crystals forming aggregates and clusters up to 1 mm in size. Due to the small size of the crystals, its macroscopic features are difficult to observe without magnification. ## Physical Properties Middendorfite crystals exhibit a luster described as vitreous to silky. The mineral is translucent. Its hardness and density have not been precisely measured due to the nature of the material. ## Colors and Varieties This mineral has a color ranging from light brown to reddish-brown. No varieties have been distinguished. ## History and Name The mineral is named in honor of the Russian traveler and naturalist of German descent, Alexander von Middendorff (1815–1894), for his contributions to the study of Siberia, where the mineral was discovered. It was found in a drill core from a borehole on the Putorana Plateau in Siberia, Russia, and described by a team of mineralogists led by Igor V. Pekov. ## Uses Middendorfite has no industrial application and is solely an object of scientific interest and a collector's item for specialists collecting rare minerals or minerals from specific localities (so-called "systematics").

Properties

Mohs hardness
3-3.5
Color
Dark to bright orange
Luster
Vitreous to silky
Streak
yellowish
Density
2.60
Cleavage
on (001)
Fracture
Sub-Conchoidal
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of middendorfite is possible only through advanced analytical methods, such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS). It is visually unrecognizable in field conditions or in a collection. Its characteristic feature is its occurrence in a specific geological environment and its association with other rare minerals. ## Differentiation from Similar Minerals It can be confused with other fine-grained, brown manganese silicates. Certain differentiation requires specialized laboratory equipment. ## Crystal Forms It forms very small, platy or fibrous crystals that combine into felted or radiating aggregates.

Geological environment

## Genesis Middendorfite forms as a result of hydrothermal processes within differentiated gabbro-dolerite intrusions. It crystallizes in vesicles and fractures within these rocks, under low-temperature conditions. ## Mineral Associations It co-occurs with minerals such as quartz, calcite, saponite, delhayelite, microcline, pectolite, apophyllite-(KF), as well as other rare minerals, e.g., putoranite and pekovite. ## Localities The only confirmed occurrence worldwide (type locality) is the Dzhaltul intrusion in the upper reaches of the Kureyka River on the Putorana Plateau, in Krasnoyarsk Krai, Siberia, Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria As a "micromount" mineral, the value of a specimen is primarily determined by the richness and quality of the aggregates visible under a microscope, as well as the presence of well-formed (though microscopic) crystals. Association with other rare minerals on the same piece of matrix rock is also important. Laboratory confirmation of identification significantly increases its value. ## Popular Localities The only source of specimens is its type locality on the Putorana Plateau in Russia, which makes every specimen from there extremely desirable for specialized collectors.

Care and storage

## Cleaning Due to its extreme rarity and the delicacy of the aggregates, mechanical cleaning is not recommended. Specimens should be protected from dust in sealed containers. If cleaning is absolutely necessary, compressed air can be used from a safe distance. ## What to Avoid Avoid contact with water, chemicals, ultrasound, and sudden temperature changes. The mineral is likely sensitive to acids. Protect it from vibrations and impacts. ## Storage Middendorfite specimens should be stored in stable conditions, in specialized "micromount" boxes or capsules, to prevent physical damage and dust accumulation. Avoid exposure to direct sunlight and moisture.

External references

Sources

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