Slyudyankaite

Chemical formula: Na₂₈Ca₄(Si₂₄Al₂₄O₉₆)(S₆+O₄)₆(S₆)₁/₃(CO₂)·₂H₂O

Slyudyankaite is a very rare, newly discovered mineral from the cancrinite group, distinguished by its intense blue color and complex chemical composition.

## Characteristics Slyudyankaite is a mineral with an intense blue color, occurring as small, irregular grains up to 1 mm in size. It is one of the newest minerals discovered in the Lake Baikal region. Its grains are usually embedded in calcitic metamorphic rocks, forming blue specks and aggregates within them. Due to its size and mode of occurrence, it does not form well-developed crystals. ## Physical Properties This mineral is characterized by a vitreous luster. It is translucent. Its Mohs hardness is 5, and its density is slightly higher than quartz, at 2.51 g/cm³. ## Colors and Varieties Slyudyankaite is known exclusively in one characteristic color – from light blue to intense blue. No varieties have been distinguished. ## History and Name The mineral's name comes from its discovery locality – the Slyudyanka River near the southern tip of Lake Baikal in Russia. It was officially recognized by the International Mineralogical Association (IMA) in 2016. The discovery was made by a team of Russian mineralogists who were studying unusual calc-silicate rocks in the region. ## Uses Due to its extreme rarity and microscopic size, slyudyankaite has no practical or commercial applications. Its significance is purely scientific and as a collector's item, as a unique representative of the cancrinite group.

Properties

Mohs hardness: 5
Luster: Vitreous
Streak: Light blue
Density: 2.51
Cleavage: None
Fracture: Uneven
Transparency: Translucent
Crystal system: Hexagonal

Diagnostic features

## Identification The key diagnostic feature is the intense blue color in the form of fine grains embedded in white, crystalline calcite (marble). The locality of origin (Slyudyanka region) is an almost certain identification indicator. ## Distinguishing from Similar Minerals Slyudyankaite can be confused with other blue minerals from the sodalite group, such as lazurite or hauyne, which also occur in marbles. Lazurite from the same region has a similar appearance, but slyudyankaite has a slightly lighter hue and a different chemical composition, verifiable only by advanced methods (EDS/WDS). In practice, without chemical analysis, differentiation is very difficult and relies mainly on the precise location of the find. ## Crystal Forms This mineral occurs as anhedral (undeveloped) grains up to 1 mm in size, forming irregular aggregates in the host rock. No euhedral crystals have been observed to date.

Geological environment

## Genesis Slyudyankaite forms as a result of contact metamorphism of carbonate rocks. It forms under high-temperature conditions within marbles (metamorphosed limestones), at the contact with alkaline rock intrusions (syenites). ## Mineral Associations This mineral co-occurs with calcite (which constitutes the main mass of the rock), diopside, phlogopite, and other rare minerals from the sodalite group, such as lazurite and vladimirivanovite. ## Localities The only confirmed locality for slyudyankaite in the world is its type locality – the Pereval quarry in the Slyudyanka River valley, on the southern shore of Lake Baikal in Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a specimen depends on the intensity and saturation of the blue color of the slyudyankaite grains, as well as their quantity and concentration in the host rock. The most desirable specimens are those where the blue grains form distinct, rich aggregates contrasting with the white background of the calcitic marble. The size of individual grains, although always small, also affects attractiveness. ## Popular Localities The only source of specimens is the Pereval quarry in Russia. Material from this locality is extremely difficult to obtain, and its acquisition and export are very limited.

Care and storage

## Cleaning Specimens containing slyudyankaite, which are typically fragments of the host rock (marble), should be cleaned with extreme caution. It is recommended to use compressed air to remove dust. Any wet cleaning is risky due to the presence of acid-soluble calcite. ## What to Avoid Contact with acids (even weak ones, like vinegar) must be absolutely avoided, as they will rapidly dissolve the host rock (calcite). Ultrasonic cleaners and strong chemical agents should not be used. The mineral is stable, but extreme temperatures should be avoided. ## Storage Specimens should be stored in a dry place, in a closed box or display case, to protect them from dust and mechanical damage. Due to the small size of the grains, storage in "micromount" boxes is recommended.

Sources

IMA Mineral List (CNMNC)