Ulfanderssonite-(Ce)

Chemical formula: (Ce³⁺₁₅Ca)Mg₂(SiO₄)₁₀(SiO₃OH)(OH,F)₅Cl₃

Ulfanderssonite-(Ce) is an extremely rare mineral from the silicate group, distinguished by its complex chemical composition and occurrence as hexagonal crystals.

## Characteristics Ulfanderssonite-(Ce) is a complex cerium, calcium, and magnesium silicate, belonging to the cerchiarite group. It forms elongated, hexagonal crystals up to 1 mm long, terminated by a pyramid. They usually occur as radial or disordered aggregates. It is a brittle mineral. ## Physical Properties The mineral is characterized by a hardness of approximately 5 on the Mohs scale and a vitreous luster. It is transparent to translucent. The calculated density is 4.83 g/cm³. ## Colors and Varieties Ulfanderssonite-(Ce) ranges in color from pale yellow to yellowish-brown. No varieties have been distinguished. ## History and Name The mineral is named in honor of Ulf B. Andersson (born 1962), a Swedish geologist and professor of petrology at Uppsala University, for his contributions to research on the Jakobsberg deposit. It was approved as a new mineral by the International Mineralogical Association (IMA) in 2017 (IMA2017-031). The type mineral is cerchiarite-(Ce). ## Uses Due to its extreme rarity, ulfanderssonite-(Ce) has no industrial applications and is solely an object of scientific interest and a collector's item for specialized collectors of rare minerals.

Properties

Mohs hardness
5-6
Color
Pinkish
Luster
Vitreous
Streak
Pale yellow
Density
4.97
Cleavage
Parallel (0 0 1)
Fracture
Irregular/Uneven
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of ulfanderssonite-(Ce) is impossible without advanced analytical methods, such as energy-dispersive spectroscopy (EDS/WDS) or X-ray diffraction (XRD). Preliminary identification based on appearance is very difficult – it can be suspected in paragenesis typical for the Jakobsberg deposit based on its yellowish color and hexagonal, acicular crystals. ## Distinguishing from Similar Minerals It can be confused with other rare cerium silicates from the Jakobsberg deposit, such as cerchiarite-(Ce) or dollaseite-(Ce). Visual differentiation is practically impossible and requires specialized chemical and structural analysis. ## Crystal Forms It forms elongated, prismatic crystals with a hexagonal cross-section, often terminated by a hexagonal pyramid. Crystals coalesce into radial or randomly arranged aggregates.

Geological environment

## Genesis Ulfanderssonite-(Ce) forms as a result of metamorphic processes in skarns. It occurs within altered iron and manganese ore deposits, in calcite-dolomite veins cutting hematite ore enriched in hausmannite. ## Mineral Associations This mineral coexists with calcite, dolomite, hausmannite, hematite, tephroite, phlogopite, as well as rarer minerals such as cerchiarite-(Ce), dollaseite-(Ce), and arsenoclasite. ## Localities The only confirmed occurrence of ulfanderssonite-(Ce) in the world is its type locality – the former Jakobsberg mine in Filipstad municipality, Värmland region, Sweden.

Rarity

Extremely rare

For collectors

## Quality Criteria The most highly valued specimens are those with well-formed, sharp crystals, forming rich, radial aggregates on a contrasting matrix (e.g., on calcite). Due to the microscopic size of the crystals, their abundance and quality visible under magnification are crucial. Any specimen with analytically confirmed presence of this mineral is extremely valuable. ## Popular Localities The only source of specimens is the Jakobsberg mine in Sweden. Material from this locality is extremely rare and sought after by collectors specializing in skarn and systematic minerals.

Care and storage

## Cleaning Utmost caution is recommended. The safest method is to use compressed air to remove dust. Any mechanical cleaning or use of liquids is discouraged due to the mineral's brittleness and rarity. ## What to Avoid Avoid contact with chemicals, acids, and ultrasonic cleaners, which can irreversibly damage the delicate crystals. The mineral is brittle, so it should be protected from impacts and vibrations. ## Storage Specimens should be stored in stable conditions, in a sealed "micromount" box, to protect them from dust, mechanical damage, and sudden temperature changes.

External references

Sources

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