Ferricerite-(LaCa)

Chemical formula: (La₆Ca₃)◻Fe³⁺(SiO₄)₃(SiO₃OH)₄(OH)₃

Ferricerite-(LaCa) is a rare lanthanide and calcium silicate from the cerite group, distinguished by its occurrence in alkaline massifs of the Kola Peninsula.

## Characteristics Ferricerite-(LaCa) is a complex silicate of lanthanides (mainly lanthanum), calcium, and iron, belonging to the cerite subgroup. It forms small, granular aggregates or poorly developed crystals. Its appearance is inconspicuous, and identification requires advanced analytical methods. ## Physical Properties This mineral is characterized by a hardness of 5 on the Mohs scale. It is relatively dense, with a specific gravity of approximately 4.7 g/cm³. It exhibits a conchoidal fracture and is translucent. The streak is white. ## Colors and Varieties Ferricerite-(LaCa) occurs in shades from pale yellow to pinkish-brown. No color or commercial varieties have been distinguished. ## History and Name The mineral's name refers to its chemical composition: the dominance of trivalent iron (Latin: *ferrum*), its belonging to the cerite group, and the dominance of lanthanum and calcium in a specific structural position. It was officially described and approved as a new mineral species in 2001. ## Applications Due to its extreme rarity, ferricerite-(LaCa) has no industrial applications. It is solely an object of scientific interest and a collector's item for specialized collectors of rare minerals.

Properties

Mohs hardness
5
Streak
White
Density
4.7
Fracture
Conchoidal
Transparency
Translucent
Crystal system
Trigonal

Diagnostic features

## Identification Visual identification of ferricerite-(LaCa) is practically impossible. Its identification relies on chemical analysis (e.g., EDS) to confirm the presence of lanthanum, calcium, and iron in appropriate proportions, and on X-ray diffraction (XRD) to determine the crystal structure. Its occurrence in a specific geological environment (alkaline massifs) is a key indicator. ## Differentiation from Similar Minerals It can be confused with other minerals from the cerite group, such as cerite-(Ce) or cerite-(La), as well as with other rare REE silicates of similar appearance. Differences can only be determined using advanced analytical techniques. ## Crystal Forms Ferricerite-(LaCa) primarily forms granular and massive aggregates. Poorly developed, small, tabular or short-prismatic crystals are rarely observed.

Geological environment

## Genesis This is a hydrothermal mineral associated with ultramafic and alkaline rocks. It forms in the late stages of crystallization of nepheline-syenite pegmatites or in hydrothermal veins cutting these massifs. ## Mineral Associations This mineral co-occurs with other minerals typical of alkaline massifs, such as eudialyte, lorenzenite, lamprophyllite, nepheline, microcline, aegirine, and other rare minerals of zirconium and rare earth elements. ## Localities The type locality (locus typicus) of ferricerite-(LaCa) is given as two closely related sites in the Khibiny Alkaline Massif on the Kola Peninsula in Russia: Mount Yukspor and Hackman Valley on that mountain. These are the only confirmed occurrences of this mineral in the world.

Rarity

Extremely rare

For collectors

## Quality Criteria For such a rare mineral, the main criterion of value is the confirmed presence itself on a fragment of the host rock. The size of ferricerite-(LaCa) aggregates and the richness of associated minerals (association) significantly increase the specimen's attractiveness. Distinct, even if poorly formed, crystals are highly desirable. ## Popular Localities The only source of ferricerite-(LaCa) specimens are the localities within the Khibiny Alkaline Massif on the Kola Peninsula in Russia. Specimens from the type locality (Mount Yukspor) are most valued by specialized collectors.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using only a soft brush to remove dust. Due to its rarity and potential instability, the use of water and any chemical agents is discouraged without absolute necessity and knowledge of the mineral's reactivity. ## What to Avoid Avoid contact with acids and other chemicals. The mineral should be protected from sudden temperature changes and direct, prolonged exposure to sunlight, which theoretically may affect its color. ## Storage It is recommended to store specimens in stable conditions, in closed display boxes, away from dust and light. It is best to keep it in its original perky box to avoid contact with other minerals and potential mechanical damage.

External references

Sources

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