Rundqvistite-(Ce)

Chemical formula: Na₃(Sr₃Ce³⁺)[Zn²⁺₂Si₈O₂₄]

Rundqvistite-(Ce) is an extremely rare cyclosilicate mineral, discovered in Sweden, distinguished by its complex chemical composition with cerium and strontium.

## Characteristics Rundqvistite-(Ce) is a cyclosilicate mineral with a very complex chemical structure. It occurs as small, tabular crystals, reaching sizes up to 0.3 x 0.2 x 0.05 mm, often forming aggregates. It is transparent and characterized by a pale blue color and vitreous luster. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of approximately 4. It has a pale blue streak and a density of 3.42 g/cm³. It exhibits perfect cleavage in one direction. ## Colors and Varieties It is observed in a uniform, pale blue color. No varieties have been distinguished. ## History and Name The mineral is named in honor of Thomas Rundqvist (born 1961), a Swedish amateur mineralogist who discovered it. It was approved by the International Mineralogical Association (IMA) in 2018 (IMA2018-043). The type locality is the Långban mine in Filipstad Municipality, Sweden. ## Uses Due to its extreme rarity and microscopic crystal sizes, Rundqvistite-(Ce) has no practical applications. It is solely an object of scientific interest and a collector's item for specialized micromineral collectors.

Properties

Mohs hardness
5-0
Color
colorless
Luster
Vitreous
Streak
white
Density
3.70
Cleavage
Perfect on {0001}
Fracture
Irregular/Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of Rundqvistite-(Ce) is almost exclusively possible using advanced analytical methods, such as Raman spectroscopy or chemical analysis with an electron microprobe (EDS/WDS). In collecting conditions, identification relies on its pale blue color, tabular crystal habit, and co-occurrence with other rare minerals from Långban. ## Distinguishing from Similar Minerals It can be confused with other pale blue, rare minerals from the type locality. Definitive differentiation from minerals with a similar appearance, such as some apatites or other silicates, requires specialized laboratory equipment. ## Crystal Forms It forms very small, thin, tabular crystals with a hexagonal outline. These crystals often occur as small aggregates.

Geological environment

## Genesis Rundqvistite-(Ce) forms in metamorphosed iron and manganese ore deposits. In its type locality (Långban), it occurs in skarns, in vugs and rock fissures. ## Mineral Associations This mineral co-occurs with minerals such as calcite, barite, hedyphane, mimetite, pyrochroite, magnetite, hausmannite, tephroite, and filipstadite. ## Localities The only confirmed occurrence of Rundqvistite-(Ce) in the world is its type locality – the historic Långban mine, in the Värmland region of Sweden. This is one of the most famous mineralogical sites in the world, renowned for the occurrence of hundreds of unique minerals.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of Rundqvistite-(Ce) specimens is primarily assessed based on the size and development of the microscopic crystals. The most desirable specimens are those with clearly visible, sharp crystals of an intense, pale blue color, set on a contrasting rock matrix. The richness of the association with other rare minerals from Långban is also important. ## Popular Localities All known specimens originate exclusively from the Långban mine in Sweden, making this locality the key and sole source of this mineral for collectors.

Care and storage

## Cleaning Specimens should be handled with the utmost care. Due to the microscopic size of the crystals, mechanical cleaning is not recommended. If absolutely necessary, compressed air can be used from a safe distance to remove dust. ## What to Avoid Avoid contact with all chemicals, acids, and detergents. The mineral is soft and brittle, so it must be protected from impacts, scratches, and vibrations. It should not be heated or subjected to ultrasound. ## Storage Specimens should be stored under stable conditions, in specialized "micromount" boxes that protect them from mechanical damage and dust. Avoid exposure to direct sunlight and extreme temperatures.

External references

Sources

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