Hedegaardite

Chemical formula: (Ca,Na)₉(Ca,Na)Mg(PO₄)₆(PO₃OH)

Hedegaardite is a rare, colorless to white mineral of the merrillite group, occurring as small grains in meteorites.

## Characteristics Hedegaardite is a phosphate mineral belonging to the merrillite group. It occurs as very small, anhedral (not exhibiting its own crystal form) grains, usually not exceeding 200 micrometers in size. It is colorless and transparent, with a vitreous luster. Due to the microscopic size of the crystals, its macroscopic features are difficult to observe. ## Physical Properties The mineral is characterized by a Mohs hardness of approximately 5. The density calculated based on the chemical formula and unit cell parameters is 3.10 g/cm³. It does not exhibit cleavage, and its fracture is uneven. It has a white streak. ## Colors and Varieties Hedegaardite is colorless to white. No colored varieties are known. ## History and Name The mineral is named in honor of Erik Hedegaard (born 1950), a Danish chemist, author, and mineral collector, who provided the material for research in which the new mineral was discovered. It was approved by the International Mineralogical Association (IMA) in 2008. The type locality is the Gujba meteorite, which fell in Nigeria in 1984. ## Uses Hedegaardite, as a microscopic and extremely rare mineral, has no practical application. It is solely an object of scientific and collecting interest in the field of meteorite mineralogy.

Properties

Mohs hardness
5
Luster
Vitreous
Streak
White
Density
3.10
Cleavage
None
Fracture
Uneven
Transparency
Transparent
Crystal system
Trigonal

Diagnostic features

## Identification Identification of hedegaardite is impossible without advanced laboratory techniques. It requires chemical analysis (electron microprobe - EDS/WDS) and structural studies (X-ray diffraction - XRD). Visually, within the meteorite matrix, it appears as microscopic, colorless grains with a vitreous luster. ## Distinguishing from Similar Minerals It can be confused with other phosphates found in meteorites, such as apatite, whitlockite, or other minerals from the merrillite group. Definitive distinction is only possible based on precise analysis of chemical composition and crystallographic data. ## Crystal Forms Hedegaardite forms only very fine, anhedral (xenomorphic) grains within the parent rock (meteorite). No well-formed crystals have been observed.

Geological environment

## Genesis Hedegaardite is a mineral of extraterrestrial origin. It forms in meteorites, specifically in Bencubbinite chondrites (CB group). Its presence is a result of processes occurring in the asteroid parent body from which the meteorite originated. ## Mineral Associations It co-occurs with other minerals typical of the Gujba meteorite, such as forsterite, enstatite, diopside, plagioclase (albite, anorthite), kamacite, troilite, chromite, and other phosphates, including apatite and whitlockite. ## Localities The only confirmed locality for hedegaardite worldwide is the Gujba meteorite, found in Yobe State, Nigeria.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a hedegaardite specimen is identical to the quality of the Gujba meteorite fragment in which it was identified. Its collector value is purely scientific and referential. A specimen is a polished thin section or mount in which the presence of the mineral has been analytically confirmed. The richness of mineral associations visible on the sample enhances its attractiveness. ## Popular Localities The only source of specimens is the Gujba meteorite (Nigeria).

Care and storage

## Cleaning Specimens (meteorite fragments) containing hedegaardite should only be cleaned with compressed air to remove dust. Due to the microscopic nature of the grains, any other method, especially mechanical or using liquids, risks their irreversible loss. ## What to Avoid Avoid contact with all chemicals, water, and ultrasound. Do not subject the specimen to sudden temperature changes. Samples should be protected from moisture, which could harm the meteorite matrix. ## Storage Meteorite fragments with hedegaardite are best stored in specialized, airtight containers such as "membrane boxes" or in padded boxes, in a dry place, away from dust and vibrations.

External references

Sources

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