Ilmajokite-(Ce)

Chemical formula: Na₁₁KBaCe³⁺₂Ti⁴⁺₁₂Si₃₇.₅O₉₄(OH)₃₀(H₂O)₂₄·5H₂O

Ilmajokite-(Ce) is a very rare, hydrated sodium, titanium, and cerium silicate, forming bright yellow, fibrous aggregates with exceptionally low hardness.

## Characteristics Ilmajokite-(Ce) is a complex, hydrated silicate belonging to the group of rare minerals. It occurs as aggregates of fine, flexible fibers and needles, often forming felt-like or matted masses. Its most characteristic feature is its intense, bright yellow color. Due to its delicate, fibrous nature and very low hardness, specimens are extremely brittle and difficult to preserve intact. ## Physical Properties This mineral is exceptionally soft, with a Mohs hardness of just 1, meaning it can be scratched with a fingernail. It is transparent to translucent. Its fibrous structure makes precise determination of luster or density difficult; density has not been measured. ## Colors and Varieties Ilmajokite-(Ce) occurs in a uniform, bright yellow color. No color varieties or commercial varieties are known. ## History and Name The mineral was discovered and described in 1972. Its name comes from the Ilmajok River, flowing near the discovery site in the Lovozero Massif on the Kola Peninsula in Russia. The "-(Ce)" suffix in the name indicates the dominant rare earth element in its chemical composition – in this case, cerium.

Properties

Mohs hardness
1
Density
0
Transparency
Transparent,Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Diagnostic features of ilmajokite-(Ce) include its unique occurrence as bright yellow, felt-like or woolly aggregates and its extremely low hardness (1 on the Mohs scale). It is very light and brittle. Its occurrence in the specific environment of alkaline pegmatites is also a key indicator. ## Distinguishing from Similar Minerals It can be confused with other secondary uranyl minerals due to its bright yellow color, but ilmajokite-(Ce) is not radioactive. It also differs from them in its extreme softness and fibrous form. Other fibrous zeolites or silicates are usually harder and have different colors. ## Crystal Forms It forms aggregates of very fine, acicular or fibrous crystals that interweave into mats, felts, or spherical aggregates. Individual, well-formed crystals are practically unknown.

Geological environment

## Genesis Ilmajokite-(Ce) is a secondary mineral, formed in the late stages of hydrothermal processes in highly differentiated alkaline pegmatites, rich in sodium and rare earth elements. It forms in voids and fractures as a product of alteration of previously crystallized, unstable minerals. ## Mineral Associations This mineral co-occurs with other rare minerals typical of Lovozero Massif pegmatites, such as belovite-(Ce), gerasimovskite, vuonnemite, lomonosovite, sphalerite, and kazakovite. ## Localities The most important and only confirmed locality for ilmajokite-(Ce) is its type locality – the Yubileinaya pegmatite in Mount Karnasurt, in the Lovozero Massif, Murmansk Oblast, Kola Peninsula, Russia.

Rarity

Very rare

For collectors

## Quality Criteria The collector's appeal of a specimen depends on the intensity and purity of the yellow color, as well as the abundance and aesthetics of the felt-like aggregates. Samples where the delicate structures of ilmajokite-(Ce) are well-preserved and contrast with the darker matrix rock are most valued. Due to its fragility, intact specimens are extremely desirable. ## Popular Localities The only source of ilmajokite-(Ce) specimens on the collector's market is the Lovozero Massif in Russia. All available samples come from this single, classic locality.

Care and storage

## Cleaning Ilmajokite-(Ce) specimens should generally not be cleaned mechanically or chemically. Any attempt to use water, a brush, or compressed air risks irreversible damage to the delicate, felt-like aggregates. It should be protected from dust. ## What to Avoid Any contact with water and chemicals should be avoided. The mineral is extremely sensitive to touch and vibrations. It must not be heated or exposed to changes in humidity, as it is a hydrated mineral and unstable in dry air. ## Storage Storage requires particular caution. The best solution is an hermetically sealed "micromount" container or a membrane box, which immobilizes the specimen without applying pressure. The container should protect against dust, moisture, and mechanical damage.

External references

Sources

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