Hollisterite

Chemical formula: Al₃Fe

Hollisterite is a naturally occurring aluminum-iron alloy, found in the Allende iron meteorite, named after the pioneer of cosmocrystallography Lincoln S. Hollister.

## Characteristics Hollisterite is a mineral from the native elements group, being a natural alloy of aluminum and iron. It was identified as microscopic, rounded grains up to 25 micrometers in size, occurring as inclusions within chromite. It is observed as an opaque mineral with a metallic luster. ## Physical Properties Due to the microscopic size of the grains, most physical properties, such as hardness, density, or fracture, have not been determined. The luster is metallic, and the mineral is opaque. ## History and Name The mineral was approved by the IMA in 2016 (IMA2016-053). Its name honors Lincoln S. Hollister (b. 1938), Professor of Earth Sciences at Princeton University, in recognition of his contributions to the fields of petrology and cosmocrystallography. It was discovered in material from the famous Allende meteorite, which fell in Mexico in 1969.

Properties

Luster
Metallic
Transparency
Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of hollisterite is possible only using advanced laboratory techniques, such as scanning electron microscopy (SEM) with chemical composition analysis (EDS) and electron backscatter diffraction (EBSD). Its characteristic chemical composition (Al₃Fe) is a key diagnostic feature. ## Distinguishing from Similar Minerals It is distinguished from other microscopic metallic phases in meteorites by its unique aluminum-to-iron ratio. ## Crystal Forms Hollisterite forms rounded, anhedral (lacking crystal faces) grains.

Geological environment

## Genesis Hollisterite formed under conditions prevalent in the early Solar System. It was found in calcium-aluminum-rich inclusions (CAIs) within the Allende carbonaceous chondrite. These inclusions are among the oldest solids formed in our planetary system. ## Mineral Associations It co-occurs with chromite, in which it forms inclusions, as well as with perovskite, hibonite, and other minerals typical of CAIs in meteorites. ## Localities The only confirmed locality for hollisterite is the Allende meteorite, which fell in Chihuahua, Mexico.

Rarity

Extremely rare

For collectors

## Quality Criteria Specimens containing hollisterite are valued solely in a scientific and collecting context as fragments of the Allende meteorite. The value of a specimen depends on the size and quality of the meteorite fragment itself, not on the presence of microscopic hollisterite, which cannot be seen with the naked eye. Fragments with visible CAIs or chondrules are most desirable.

Care and storage

## Cleaning Due to its occurrence as microscopic inclusions within other minerals (matrix), individual hollisterite grains are not subject to cleaning. ## What to Avoid Meteorite specimens containing hollisterite should be protected from moisture, which can cause oxidation of iron minerals. Contact with strong acids and chemicals should be avoided. ## Storage Storage in a dry environment, preferably in a sealed container with a desiccant, is crucial for preserving the integrity of the specimen-matrix.

External references

Sources

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