Tadzhikite-(Y)

Chemical formula: Ca<sub>3</sub>(Y,Ce)<sub>2</sub>(Ti,Al,Fe<sup>3+</sup>)B<sub>4</sub>Si<sub>4</sub>O<sub>22</sub>

Tadzhikite-(Y) is a rare borosilicate of calcium, titanium, and ytterbium, forming small, prismatic, brown crystals.

## Characteristics Tadzhikite-(Y) is a complex borosilicate from the hellandite group, occurring as small, prismatic crystals that rarely exceed a few millimeters in length. It typically forms radial or fibrous aggregates. Its crystals are elongated and often show striations on their faces. ## Physical Properties The mineral is characterized by a hardness of 5-6 on the Mohs scale and a vitreous luster. It is brittle, and its density is approximately 3.81 g/cm³. It is transparent to translucent. ## Colors and Varieties The typical color of tadzhikite-(Y) is brown in various shades, from light brown to reddish-brown. No distinct color varieties or commercial forms are recognized. ## History and Name The mineral's name comes from its discovery locality in Tajikistan. It was first described in 1969 by A. F. Efimov and colleagues. The -(Y) suffix in the name indicates the dominance of ytterbium (Y) in its chemical composition, in accordance with rare-earth mineral naming conventions.

Properties

Mohs hardness
5-6
Luster
Vitreous
Streak
White
Density
3.81
Cleavage
Good on {110}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Amateur identification of tadzhikite-(Y) is practically impossible and requires advanced analytical methods, such as chemical analysis (EDS/WDS) and X-ray diffraction (XRD). Preliminary identification is based on the specific geological environment (alkaline pegmatites), crystal habit, and associated minerals. ## Distinguishing from similar minerals It can be confused with other minerals from the hellandite group, such as hellandite-(Y) or cappelenite-(Y). Differentiation is only possible based on detailed chemical analysis. ## Crystal forms It forms elongated, prismatic crystals, often gathered in radial or fibrous aggregates. Crystals may be terminated by steeply inclined pyramid faces.

Geological environment

## Genesis It is a mineral of magmatic origin, crystallizing in the late stages within alkaline pegmatites, rich in rare-earth elements, boron, and titanium. ## Mineral associations It co-occurs with minerals such as eudialyte, microcline, aegirine, nepheline, stillwellite-(Ce), quartz, and other rare-earth minerals. ## Localities The most important and type locality for this mineral is the Alai Range massif in Tajikistan. It has also been reported in the Dara-i-Pioz alkaline complex in Tajikistan and in Norway (Langesundsfjorden).

Rarity

Very rare

For collectors

## Quality criteria The collector quality of tadzhikite-(Y) primarily depends on the crystal habit and size. Well-formed, single crystals or aesthetic aggregates on matrix are most valued. Due to the microscopic nature of most specimens, any well-visible crystal is valuable. Purity and intensity of color are of secondary importance. ## Popular localities The vast majority, if not all, collector specimens originate from pegmatites in the Alai Range massif in Tajikistan.

Care and storage

## Cleaning Cleaning with compressed air or a very soft brush is recommended. Due to the rarity and fragility of the specimen, contact with water and chemical agents should be avoided. ## What to avoid Ultrasonic cleaners, all acids, and detergents should be avoided. The mineral is sensitive to sudden temperature changes and mechanical damage. ## Storage Tadzhikite-(Y) specimens should be stored in stable conditions, in sealed "micromount" boxes, away from dust, moisture, and direct sunlight to prevent potential damage.

Sources

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