Hopmannite

Chemical formula: Ba₂(Ti⁴⁺₅Fe²⁺)O₁₃

Hopmannite is an extremely rare barium, titanium, and iron oxide mineral, discovered in the NWA 14628 meteorite.

## Characteristics Hopmannite is an oxide mineral, identified as microscopic inclusions up to 20x50 μm in size. It occurs as elongated, lath-like crystals alongside other rare minerals within the meteorite. Its occurrence is exclusively limited to extraterrestrial material, making it a subject of scientific research rather than a collectible object in the traditional sense. ## Physical Properties Due to the microscopic size of the crystals, most physical properties, such as hardness, density, or luster, have not been determined. Observations under an electron microscope indicate a metallic or submetallic luster in reflected light. ## Colors and Varieties The observed crystals are opaque and gray in color. No varieties of this mineral have been distinguished. ## History and Name The name hopmannite honors Christian Hopmann, a German meteorite collector who provided the NWA 14628 meteorite specimen for research, in which the mineral was discovered. The mineral and its name were approved by the International Mineralogical Association (IMA) in 2022 (IMA2022-038). The discovery was made by a research team led by Chi Ma. ## Applications Hopmannite has no practical applications. Its significance is purely scientific, providing information about mineralogical processes occurring in celestial bodies.

Properties

Mohs hardness
5-5.5
Color
black to dark-grey
Luster
Metallic
Streak
gray
Density
4.15
Cleavage
along (100)
Fracture
Irregular/Uneven
Transparency
Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of hopmannite is possible only through advanced laboratory techniques, such as scanning electron microscopy (SEM) combined with chemical composition analysis (EDS) and electron backscatter diffraction (EBSD). It is not possible to identify it visually or by amateur methods. ## Distinguishing from Similar Minerals Due to its unique chemical composition and crystal structure, it is easily distinguishable from other titanium minerals using analytical methods. It occurs in association with other rare titanium minerals, such as maoit and tistarite. ## Crystal Forms It forms elongated, lath-like crystals with sizes not exceeding several tens of micrometers.

Geological environment

## Genesis Hopmannite is a mineral of extraterrestrial origin. It formed as a result of processes occurring within the parent body of an ureilite achondrite – likely under conditions of high temperature and pressure during impact or metasomatic processes within the asteroid. It is a late-stage mineral, crystallizing in veins of carbonaceous material. ## Mineral Associations It co-occurs with graphite, maoit, tistarite, daubréelite, troilite, iron-nickel alloys, and silicates typical of ureilites (olivine, pyroxene). ## Localities The only known occurrence (type locality) is the ureilite achondrite, ungrouped meteorite NWA 14628, found in the Dakhla region of Western Sahara.

Rarity

Extremely rare

For collectors

## Quality Criteria Not applicable. Hopmannite does not occur in collectible specimen form. Its value is purely scientific, and the only object that might enter the market is a fragment of the NWA 14628 meteorite in which this mineral was identified. The value of such a fragment depends on its mass and provenance, not on the presence of microscopic hopmannite inclusions. ## Popular Localities The only source is the NWA 14628 meteorite.

Care and storage

## Cleaning Not applicable. The mineral occurs exclusively as microscopic inclusions within the meteorite rock and is not isolated. ## What to Avoid Not applicable. The parent specimen (meteorite) should be protected from moisture, chemicals, and contaminants to preserve the integrity of all minerals contained within it. ## Storage Storage pertains to the entire meteorite specimen. It should be kept under stable conditions, preferably in a dry environment (e.g., in a container with a desiccant), away from direct sunlight and contaminants.

External references

Sources

Read more