Mendeleevite-(Nd)

Chemical formula: Cs₆(Nd,REE,Ca)₃₀(Si₇₀O₁₇₅)(OH,F,H₂O)₃₅

Mendeleevite-(Nd) is a very rare mineral from the mendeleevite group, characterized by a complex silicate structure and the presence of cesium and neodymium.

## Characteristics Mendeleevite-(Nd) is an extremely rare mineral with a very complex chemical composition, belonging to the silicates. It forms small, tabular or platy crystals, reaching sizes up to 0.3 x 0.2 x 0.05 mm. It usually occurs as granular aggregates or irregular intergrowths. It is vitreous and has a light brown color. ## Physical Properties This mineral is characterized by a hardness of approximately 5 on the Mohs scale. It has a vitreous luster, and its crystals are translucent. The density of mendeleevite-(Nd) is approximately 3.34 g/cm³. ## Colors and Varieties It has only been observed in a light brown color. No varieties have been distinguished. ## History and Name The mineral's name honors Dmitri Mendeleev (1834-1907), a Russian chemist and creator of the periodic table of elements. The suffix -(Nd) refers to the dominant rare earth element in its composition – neodymium. The mineral was approved by the IMA in 2010, and its discovery was described by I.V. Pekov, N.V. Chukanov, and others in 2011. ## Applications Due to its extreme rarity and microscopic crystal sizes, mendeleevite-(Nd) has no practical applications. It is solely an object of scientific and collecting interest for specialized micromineral collectors.

Properties

Mohs hardness: 5
Luster: Vitreous
Streak: White
Density: 3.34
Cleavage: None
Fracture: Uneven
Transparency: Translucent
Crystal system: Trigonal

Diagnostic features

## Identification Identification of mendeleevite-(Nd) is impossible without advanced analytical techniques, such as electron spectroscopy (EDS/WDS) to confirm the complex chemical composition with a dominance of cesium and neodymium. Visually, at the occurrence site, it can be suspected based on its light brown color and association with other rare minerals of the Dara-i-Pioz massif. ## Distinguishing from Similar Minerals It can be confused with other minerals from the mendeleevite group, such as mendeleevite-(Ce). Differentiation requires chemical analysis to determine the dominant rare earth element. From other light brown minerals from the type locality, it is distinguished by its unique chemical composition. ## Crystal Forms It forms very small, thin, tabular crystals with a hexagonal outline. It also occurs as irregular granular aggregates and clusters.

Geological environment

## Genesis This mineral forms under hydrothermal conditions, within syenite pegmatites rich in rare earth elements and alkalis. Its occurrence is associated with the unique geological environment of the Dara-i-Pioz glacial massif. ## Mineral Associations It co-occurs with minerals such as quartz, microcline, aegirine, polylithionite, tadzhikite-(Ce), kapranovite-(Ce), and turkestanite. ## Localities The only confirmed locality of mendeleevite-(Nd) in the world is its type locality – the Dara-i-Pioz Glacier in the Alay Mountains, Tajikistan.

Rarity

Extremely rare

For collectors

## Quality Criteria For micromineral collectors, the most valuable specimens are those with well-formed, sharp crystals with a hexagonal outline, even if they are microscopic in size. An aesthetic composition with associated minerals, such as aegirine or polylithionite, which can form an attractive background, is also important. Purity and lack of damage are crucial. ## Popular Localities The only source of specimens is the Dara-i-Pioz Glacier in Tajikistan, which is known for yielding many unique and rare minerals.

Care and storage

## Cleaning Specimens should only be cleaned with compressed air to remove dust. Due to the microscopic size of the crystals and their fragility, any mechanical contact, including with brushes or water, should be avoided. ## What to Avoid Avoid contact with chemicals, ultrasonics, and sudden temperature changes. The mineral is brittle and susceptible to mechanical damage. ## Storage It is recommended to store specimens exclusively in specialized "micromount" boxes, which protect them from dust, shocks, and damage. Avoid exposure to direct sunlight, although there is no evidence of fading.

Sources

IMA Mineral List (CNMNC)