Dellagiustaite

Chemical formula: V²⁺Al₂O₄

Dellagiustaite is an extremely rare mineral from the spinel group, distinguished by the presence of vanadium in the +2 oxidation state (V²⁺).

## Characteristics Dellagiustaite is a mineral from the spinel group, chemically defined as vanadium(II) aluminate. It occurs as microscopic, subhedral (partially formed) grains, usually not exceeding 100 micrometers in size. These grains are most often intergrown with other minerals, mainly hibonite and spinel. Due to its size, visual features visible to the naked eye cannot be observed. ## Physical Properties Due to the microscopic size of the crystals, most physical properties, such as hardness, density, or luster, have not been precisely measured, but only estimated based on its chemical composition and belonging to the spinel group. The luster is likely vitreous. ## Colors and Varieties Observed dellagiustaite grains are dark gray to black. The mineral is opaque. No varieties have been distinguished. ## History and Name The mineral was officially recognized by the International Mineralogical Association (IMA) in 2018 (IMA2018-058). Its name honors Antonio Dellagiusta, a professor of mineralogy at the University of Padua (Italy), for his contribution to the crystal chemistry of spinels. It was discovered in samples from the Allende meteorite, which fell in Mexico in 1969. ## Uses Dellagiustaite has no commercial or industrial applications. Its significance is purely scientific, as an indicator of the extremely reducing conditions of the early Solar System's formation.

Properties

Mohs hardness
6.5-7
Color
black
Luster
Vitreous
Streak
black
Density
4.6
Cleavage
None
Fracture
Irregular/Uneven,Splintery
Transparency
Opaque
Crystal system
Isometric

Diagnostic features

## Identification Identification of dellagiustaite is impossible without advanced analytical techniques. It requires the use of an electron microscope with an energy-dispersive spectrometer (EDS/WDS) to determine the chemical composition, and X-ray diffraction (XRD) or electron backscatter diffraction (EBSD) to confirm the crystal structure. It occurs as microscopic, dark gray inclusions in other minerals within the Allende meteorite. ## Distinguishing from Similar Minerals Visually, it is indistinguishable from other dark, opaque minerals of the spinel group, such as hercynite, chromite, or spinel (MgAl₂O₄) itself, with which it often coexists. The key is to confirm the dominance of vanadium (V²⁺) in its chemical composition. ## Crystal Forms Crystals have the form of subhedral (imperfectly formed) grains, typically with shapes resembling an octahedron, which is characteristic of minerals from the spinel group. They occur as single, isolated grains intergrown with other mineral phases.

Geological environment

## Genesis Dellagiustaite forms under conditions of extremely low oxygen fugacity, i.e., in a strongly reducing environment. Such conditions prevailed in the solar nebula from which the earliest solid components of the Solar System formed. This mineral crystallizes at high temperatures as one of the primary phases in calcium-aluminum-rich inclusions (CAIs) in carbonaceous chondrites. ## Mineral Associations This mineral has been found in direct association with hibonite, spinel (MgAl₂O₄), perovskite, melilite, and rare vanadium-bearing minerals such as davisite and vanadoallite. It coexists with other minerals typical of CAIs in the Allende meteorite. ## Localities The only confirmed locality of dellagiustaite worldwide is the Allende meteorite. This is a CV3 carbonaceous chondrite that fell on February 8, 1969, in Chihuahua, Mexico. The mineral was identified in a CAI designated as "Fluffy Type A" (FTA) named "Curious Marie".

Rarity

Extremely rare

For collectors

## Quality Criteria As a mineral impossible to observe with the naked eye, dellagiustaite does not have typical quality criteria used for collectible specimens, such as color, luster, or crystal size. Its value is purely scientific and contextual. For meteorite collectors, the value of a specimen lies in possessing a fragment of the Allende meteorite in which the presence of this mineral has been documented. Dellagiustaite itself is merely a microscopic curiosity. ## Popular Localities The only known locality is the Allende meteorite. Fragments of this meteorite are available on the collector's market, but those containing confirmed dellagiustaite are almost exclusively found in research institutions.

Care and storage

## Cleaning Specimens containing dellagiustaite (mainly fragments of the Allende meteorite) are stable, but due to their scientific value and the potential sensitivity of other components, wet cleaning is not recommended. Any dust can be removed very carefully with a soft brush or a photographic air blower. ## What to Avoid Avoid contact with water, chemicals, and ultrasound. Meteorites may contain minerals soluble in water or susceptible to oxidation. They should be protected from moisture and sudden temperature changes. ## Storage Samples with dellagiustaite, as fragments of a valuable meteorite, should be stored under stable conditions, preferably in a sealed, dry container (e.g., a "membrane box" or a box with a desiccant). Avoid direct exposure to sunlight and keep them away from sources of contamination.

External references

Sources

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