Jørgensenite

Chemical formula: Na₂Sr₁₄Na₂Al₁₂F₆₄(OH)₄

Jørgensenite is a very rare sodium, strontium, and aluminum fluoride, forming colorless, tabular crystals.

## Characteristics Jørgensenite is an extremely rare mineral from the fluoride group. It occurs as small, colorless, tabular crystals, reaching sizes up to 1 x 0.5 x 0.1 mm. It typically forms aggregates or occurs as inclusions in other minerals, mainly in cryolite. It is transparent and characterized by a vitreous luster. ## Physical Properties This mineral has a hardness of approximately 3.5 on the Mohs scale. Its crystals exhibit perfect cleavage in one direction. The density of jørgensenite is approximately 4.05 g/cm³. ## History and Name Jørgensenite was discovered in the Ilímaussaq intrusive complex in Greenland, its only confirmed locality. Approved as a new mineral by the IMA in 1997, it was named in honor of Vilhelm Jørgensen (1844-1925), a Danish chemist and director of the cryolite mine in Ivittuut, for his contributions to the study of minerals from this locality.

Properties

Mohs hardness: 3.5
Luster: Vitreous
Streak: White
Density: 4.05
Cleavage: Perfect on {001}
Fracture: Uneven
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of jørgensenite is extremely difficult without advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS/WDS). Preliminary identification is based on its unique occurrence environment (pegmatites in the Ilímaussaq complex), co-occurrence with minerals such as cryolite and jarlite, and the tabular form of colorless crystals. ## Distinguishing from Similar Minerals It can be confused with other colorless fluorides from this locality, such as jarlite, thomsenolite, or pachnolite. Differentiation requires specialized studies, as visual features are very similar. Jørgensenite is distinguished by its unique chemical composition and crystallographic parameters. ## Crystal Forms It forms thin, tabular crystals with a pseudohexagonal habit, often grouped into small aggregates. Crystals are usually very small, rarely exceeding 1 mm.

Geological environment

## Genesis Jørgensenite forms in the late stage of crystallization in the unique environment of nepheline-sodalite pegmatites, rich in fluorine. It is a product of hydrothermal processes occurring within alkaline intrusions. ## Mineral Associations This mineral occurs in close association with cryolite, jarlite, stenonite, weberite, as well as rare fluorides such as bøggildite and usovite. It is often found as inclusions in cryolite. ## Localities The only known and confirmed locality of jørgensenite in the world is the Ilímaussaq alkaline complex in southern Greenland.

Rarity

Extremely rare

For collectors

## Quality Criteria As a "micromount" mineral, the value of a specimen is primarily determined by the certainty of its identification. Specimens with well-formed, sharp crystals, even if microscopic in size, are most highly prized. Association with other rare minerals from this locality is also important. ## Popular Localities All collector material comes from a single location - the Ilímaussaq complex in Greenland. Specimens are available exclusively on the specialized market and originate from old collections or rare finds.

Care and storage

## Cleaning Due to its extreme rarity and small crystal size, mechanical cleaning is not recommended. If necessary, compressed air can be used to remove dust. Avoid contact with water and chemicals. ## What to Avoid Avoid all acids and strong bases, which can damage the mineral. It is sensitive to sudden temperature changes and mechanical damage due to its cleavage and relatively low hardness. ## Storage Jørgensenite specimens should be stored under stable conditions, in specialized "micromount" boxes, protecting them from dust, moisture, and physical damage. Avoid exposure to direct sunlight.

Sources

IMA Mineral List (CNMNC)