Delhuyarite-(Ce)

Chemical formula: Ce³⁺₄Mg(Fe³⁺₂W⁶⁺)&#₉₇₂₃;(Si₂O₇)₂O₆(OH)₂

Delhuyarite-(Ce) is a very rare mineral from the sorosilicate group, characterized by a complex chemical composition containing cerium, magnesium, iron, and tungsten.

## Characteristics Delhuyarite-(Ce) is an extremely rare mineral that forms very small, tabular or platy crystals, reaching up to 0.3 mm in size. They typically occur as radial or randomly oriented aggregates. The mineral is brittle, and due to the small size of the crystals, most of its physical properties are difficult to determine precisely without specialized equipment. ## Physical Properties Crystals exhibit a luster described as vitreous to resinous. The Mohs hardness is estimated to be around 5. The mineral is translucent. The density calculated based on the chemical formula and unit cell parameters is 5.45 g/cm³. ## Colors and Varieties Delhuyarite-(Ce) has a characteristic reddish-brown to brown color. The streak of this mineral is light brown. No varieties have been distinguished. ## History and Name The mineral was first described in 2016 by a group of researchers (U. Hålenius et al.) based on material from the Nya Bastnäs mine in Riddarhyttan, Västmanland County, Sweden. The name "delhuyarite" honors the brothers Fausto and Juan José de Elhuyar, Spanish chemists and mineralogists who first isolated metallic tungsten in 1783. The suffix "-(Ce)" refers to cerium as the dominant rare earth element in the mineral's chemical composition.

Properties

Mohs hardness: 5
Color: Brown black
Luster: Vitreous to resinous
Streak: Dark brown
Density: 5.20
Cleavage: Good on {100}
Fracture: Uneven
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of delhuyarite-(Ce) is practically only possible using advanced analytical methods, such as electron spectroscopy (EDS/WDS) and X-ray diffraction (XRD), due to its unique chemical composition. Visually, it is a reddish-brown mineral forming very small, radial aggregates. ## Distinguishing from Similar Minerals It may be confused with other rare cerium silicates or minerals from the cewinite group, to which it is related. Definitive distinction requires chemical analysis to confirm the presence and proportions of magnesium, iron, and tungsten. ## Crystal Forms Crystals are very small, with a maximum length of 0.3 mm. They take the form of thin tablets or lamellae, often combining into radial or disordered aggregates.

Geological environment

## Genesis Delhuyarite-(Ce) forms in magnesian skarns that have undergone sodic metasomatism. It occurs within dolomite-calcite fillings of small fissures and voids in the skarn. ## Mineral Associations This mineral coexists with calcite, dolomite, fluorite, cuprite, hematite, anthophyllite, phlogopite, cewinite-(Ce), bastnäsite-(Ce), and ferriallanite-(Ce). ## Localities The only confirmed locality for delhuyarite-(Ce) in the world is its type locality – the historical mining fields of Nya Bastnäs in Riddarhyttan, Skinnskatteberg Municipality, Västmanland County, Sweden.

Rarity

Extremely rare

For collectors

## Quality Criteria As a "micromount" mineral, the collector's value of a specimen primarily depends on the richness and development of microscopic crystals within the field of view. Most desirable are specimens with distinct, radial aggregates of reddish-brown crystals, well-contrasted with the surrounding rock (matrix). Association with other rare minerals from this locality is also important.

Care and storage

## Cleaning Due to its extreme rarity and small crystal size, mechanical cleaning is not recommended. If absolutely necessary, compressed air can be used to remove loose dust particles. Avoid contact with water and chemicals. ## What to Avoid Avoid all chemicals, acids, and ultrasonics. The crystals are very small and brittle, so they should be protected from shocks, friction, and sudden temperature changes. ## Storage Delhuyarite-(Ce) specimens should be stored exclusively in specialized "micromount" boxes, protecting them from mechanical damage and dust. Avoid exposure to sunlight, although there is no specific data on its effect on the mineral.

External references

https://www.mindat.org/min-51415.html