Calcybeborosilite-(Y)

Chemical formula: (Y,REE,Ca)<sub>2</sub>(B,Be)<sub>2</sub>(SiO<sub>4</sub>)<sub>2</sub>(OH,O)<sub>2</sub>

Calcybeborosilite-(Y) is a very rare mineral from the gadolinite group, forming small, prismatic crystals with a vitreous luster.

## Characteristics Calcybeborosilite-(Y) is an extremely rare silicate from the gadolinite group, containing yttrium, calcium, boron, and beryllium. It occurs as very small, elongated, prismatic crystals, rarely exceeding 1 mm in length. It typically forms radial or tangled aggregates. Due to its size and rarity, its visual characteristics are difficult to assess without magnification. ## Physical Properties Crystals exhibit a vitreous luster. The mineral is brittle, and its Mohs hardness is approximately 5.5-6. It is a relatively dense mineral, which is typical for silicates containing rare earth elements. ## Colors and Varieties Observed crystals are usually colorless, white, or have a pale yellow tint. No varieties of this mineral have been distinguished. ## History and Name The mineral's name refers to its chemical composition: **Cal**cium, **Be**ryllium, **Bo**ron, and **Sil**icon. The suffix "-(Y)" indicates the dominant rare earth element – yttrium. It was first described in 1999 by A.V. Voloshin, V.V. Subbotin, V.Y. Gorkhovenko, Y.P. Menshikov, A.Y. Litoshenko, and N.V. Chukanov based on samples from the Oleniy massif on the Kola Peninsula in Russia.

Properties

Mohs hardness
5.5-6
Luster
Vitreous
Streak
White
Density
3.6-3.76
Cleavage
Good on {001}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of this mineral is possible only through advanced laboratory methods, such as chemical analysis (EDS/WDS) and X-ray powder diffractometry (XRD). In collector conditions, identification relies on trust in a label from a reputable source, especially since specimens come from a single, specific location. ## Distinguishing from Similar Minerals It can be confused with other minerals from the gadolinite group, such as gadolinite-(Y) or datolite, which may occur in similar environments. Visual differentiation is practically impossible and requires specialized chemical analysis, especially to confirm the presence of boron and beryllium. ## Crystal Forms It forms small, prismatic, elongated crystals, often grouped into radial or chaotic aggregates. Crystals are usually very small, reaching up to 1 mm in length.

Geological environment

## Genesis Calcybeborosilite-(Y) forms in the late stages of hydrothermal processes associated with alkaline nepheline-syenite pegmatites. It crystallizes in rock fissures and voids. ## Mineral Associations This mineral co-occurs with other rare minerals, such as microcline, quartz, albite, nepheline, aegirine, catapleiite, fluorite, and especially with other boron and beryllium minerals, like datolite. ## Localities The only confirmed occurrence (type locality) of this mineral in the world is the Oleniy massif (Oleniy Ruchey) on the Kola Peninsula in the Murmansk Oblast, Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a specimen primarily depends on the richness and size of the crystal aggregates on the rock matrix. The most desirable specimens are those with clearly visible, though still microscopic, radial crystal clusters, contrasting well with the host rock. Due to its extreme rarity, any authenticated specimen holds high value for specialized collectors of rare and systematic minerals. ## Popular Localities The only source of specimens is the type locality – the Oleniy massif on the Kola Peninsula in Russia. All specimens available on the collector's market originate from this single location.

Care and storage

## Cleaning Due to the extreme rarity and small size of the crystals, mechanical cleaning is not recommended. If absolutely necessary, compressed air can be used to remove dust. Avoid contact with water and chemicals. ## What to Avoid Avoid ultrasound, chemical agents, high temperatures, and any mechanical stress that could damage the delicate crystals or the host rock. ## Storage Specimens should be stored exclusively in specialized collector's boxes (so-called "micromount boxes"), protecting them from dust, shock, and light. Display should be away from direct sunlight and heat sources.

Sources

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