Västmanlandite-(Ce)

Chemical formula: Ce³⁺₃CaMg₂Al₂Si₅O₁₉(OH)₂F

A rare sorosilicate mineral, characterized by its occurrence as dark brown, tabular crystals in skarns.

## Characteristics Västmanlandite-(Ce) is a very rare mineral belonging to the sorosilicate group of gatelite. It forms small, tabular or platy crystals, usually with a hexagonal outline, reaching sizes of up to several millimeters. It most commonly occurs as aggregates embedded in rock. It is a dark mineral, ranging in color from reddish-brown to almost black. ## Physical Properties Västmanlandite-(Ce) crystals exhibit a hardness of approximately 6 on the Mohs scale. They have a vitreous to resinous luster. They are brittle, and their density is about 4.2 g/cm³. The mineral is translucent only on thin edges, remaining opaque in mass. ## Colors and Varieties This mineral is monochromatic – it occurs in shades of dark brown, reddish-brown, and black. No color varieties or commercial varieties have been distinguished for it. ## History and Name The mineral's name comes from the historical province of Västmanland in Sweden, where its type locality, the Malmkärra mine, is located. It was formally described and approved as a new mineral species by the International Mineralogical Association (IMA) in 2000. The "(Ce)" suffix in the name indicates cerium as the dominant rare earth element in its chemical composition. ## Uses Västmanlandite-(Ce) has no industrial applications. Its significance is purely scientific and as a collector's item, as a rare and well-defined mineralogical species.

Properties

Mohs hardness
6
Color
Dark brown
Luster
Resinous to vitreous
Streak
Yellowish grey
Density
0
Cleavage
Parallel to (100).
Fracture
Irregular/Uneven,Conchoidal
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of västmanlandite-(Ce) under amateur conditions is practically impossible. It requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical microanalysis (EDS/WDS) to confirm its composition and crystal structure. Preliminary field identification is based on its dark brown color, tabular crystal form, and specific geological environment (skarns). ## Distinguishing from Similar Minerals This mineral can be confused with other dark minerals found in skarns, such as some garnets (andradite), epidotes (allanite), pyroxenes, or amphiboles. Differentiation is based on crystal form (hexagonal outline), luster, and hardness, but only laboratory analysis provides certainty. ## Crystal Forms Västmanlandite-(Ce) crystallizes as thin to thick tablets, often with a hexagonal outline. Crystals are usually small, not exceeding a few millimeters, and are often embedded in the surrounding rock (matrix).

Geological environment

## Genesis Västmanlandite-(Ce) is a metamorphic mineral. It forms in skarns, which are carbonate rocks that have undergone alteration due to high temperature and pressure in contact with magmatic intrusions. Its crystallization is associated with metasomatism, a process of chemical exchange of components between carbonate rock and hot solutions. ## Mineral Associations This mineral coexists with other minerals typical of the skarn environment. In its type locality (Malmkärra mine), it was found in association with tremolite, talc, magnetite, chalcopyrite, fluorite, dollaseite-(Ce), and allanite-(Ce). ## Localities This is an extremely rare mineral, known from only a few localities worldwide. The most important and type locality is the Malmkärra mine in Norberg municipality, Västmanland region, Sweden. Outside Sweden, its occurrence has also been reported in the Buca della Vena mine in Tuscany, Italy.

Rarity

Very rare

For collectors

## Quality Criteria The quality of a västmanlandite-(Ce) specimen primarily depends on the degree of crystal development and size. Specimens with sharp, well-defined, undamaged crystals with a distinct hexagonal outline are most valued. The contrast with the surrounding rock (matrix) and the presence of associated minerals confirming the paragenesis are also important. ## Popular Localities The only source of collector specimens of some significance is the type locality – the Malmkärra mine in Sweden. Specimens from this location are historically and scientifically most important and serve as a reference point for this mineral.

Care and storage

## Cleaning Specimens should only be cleaned mechanically, using a soft, dry brush to remove dust. Due to its rarity and potential reactivity, avoiding contact with water and chemicals is the safest approach. ## What to Avoid Avoid contact with any acids and chemicals that could damage the mineral's surface. It should not be heated or subjected to ultrasound. Prolonged exposure to strong sunlight is not recommended. ## Storage Västmanlandite-(Ce) specimens are best stored in stable conditions, in closed display or cabinet boxes, protecting them from dust, moisture, and sudden temperature changes. Due to its brittleness, avoid placing it in contact with harder minerals.

External references

Sources

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