Polyakovite-(Ce)

Chemical formula: (Ce₃+,Ca)₄MgCr₃+₂(Ti₄+,Nb₅+)₂Si₄O₂₂

Polyakovite-(Ce) is a very rare mineral from the chevkinite group, characterized by a complex chemical composition containing cerium, magnesium, chromium, and titanium.

## Characteristics Polyakovite-(Ce) is an extremely rare mineral belonging to the chevkinite group and chevkinite supergroup. It occurs as very fine, columnar or acicular crystals, usually not exceeding 1 mm in size, forming irregular aggregates. It is black and opaque, with a submetallic luster. ## Physical Properties This mineral is characterized by a Mohs hardness of 6. It has a black color and a black streak. Its crystals exhibit poor cleavage. It is brittle, and its fracture is uneven. ## History and Name Polyakovite-(Ce) was first described in 1991 by N.V. Chukanov and co-workers. Its name honors Vladislav Olegovich Polyakov (1950–1993), a Russian mineralogist from the Ilmen Reserve. The suffix "-(Ce)" indicates the dominance of cerium as the rare earth element in its composition. The type locality, from which it originates, is Ice Mine No. 2 in the Ilmen Massif, Southern Urals, Russia.

Properties

Mohs hardness: 6
Luster: Sub-Metallic
Streak: Black
Density: 4.28
Cleavage: Poor/Indistinct
Fracture: Uneven
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of Polyakovite-(Ce) is impossible without advanced analytical techniques, such as energy-dispersive spectroscopy (EDS) or electron microprobe analysis (EMPA). It is visually indistinguishable in the field or in a collection. ## Distinguishing from similar minerals It can be confused with other black, fine-grained accessory minerals occurring in similar parageneses, such as ilmenite, magnetite, or other minerals from the chevkinite group. Definitive differentiation requires specialized chemical composition studies. ## Crystal forms It forms very small, prismatic or acicular crystals, often grouped into irregular aggregates.

Geological environment

## Genesis Polyakovite-(Ce) forms in carbonatite veins (sovites) cutting fenitized gneisses. It is a mineral of magmatic origin, associated with metasomatic processes in alkaline complexes. ## Mineral associations At the type locality, it co-occurs with calcite, phlogopite, apatite, pyrochlore, zircon, and miaskite (a variety of nepheline). ## Localities The only confirmed occurrence of this mineral in the world is its type locality - Ice Mine No. 2 in the Ilmen Massif, Chelyabinsk Oblast, Southern Urals, Russia.

Rarity

Extremely rare

For collectors

## Quality criteria As a "micromount" mineral, its collector value primarily depends on the confirmation of its identity through analysis. The most valuable specimens are those where the crystals, despite their small size, are well-formed and clearly visible against the matrix rock. The richness of associations with other rare minerals also increases the attractiveness of the specimen.

Care and storage

## Cleaning Due to its extreme rarity and small crystal size, specimens typically do not require cleaning and should be left undisturbed. If absolutely necessary, a soft brush can be used to remove dust. ## What to avoid Avoid contact with chemicals, ultrasonics, and any mechanical cleaning methods that could damage the delicate crystals or matrix rock. ## Storage Specimens should be stored under stable conditions, in sealed "micromount" boxes, to protect them from dust, vibrations, and mechanical damage. Avoid exposure to extreme temperatures.

Sources

IMA Mineral List (CNMNC)