Burnettite

Chemical formula: CaV<sup>3+</sup>AlSiO<sub>6</sub>

Burnettite is a rare, dark green clinopyroxene mineral, found exclusively in calcium-aluminum-rich meteorites.

## Characteristics Burnettite is a clinopyroxene mineral, belonging to the vanadium pyroxenes. It forms very small, anhedral (not exhibiting its own crystallographic forms) grains, usually not exceeding 20 micrometers in size. It occurs as a component of calcium-aluminum-rich inclusions (CAIs) in carbonaceous chondrites. Its color is dark green, and due to the microscopic size of the crystals, most physical properties are difficult to observe with the naked eye. ## Physical Properties Due to the microscopic size of its grains, many physical properties of burnettite, such as hardness, density, luster, or fracture, have not been precisely measured. Hardness is estimated based on similar pyroxenes to be approximately 6 on the Mohs scale. Luster is described as vitreous. ## Colors and Varieties This mineral is characterized by a dark green color. No varieties are known. ## History and Name Burnettite was first described in 2013 after being found in a type B inclusion (named "Inclusion 5") in the Allende meteorite, which fell in Mexico in 1969. The mineral's name honors Donald S. Burnett, a professor of cosmochemistry at the California Institute of Technology, for his contributions to research on processes occurring in the early Solar System. ## Uses Burnettite has no commercial or industrial applications. Its significance is purely scientific, serving as an indicator of the physicochemical conditions prevailing in the solar nebula during the formation of the oldest solid bodies in our Solar System.

Properties

Mohs hardness
6
Luster
Vitreous
Streak
Light green
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of burnettite is possible only through advanced laboratory techniques, such as electron microprobe analysis (EMPA) and spectroscopy. It is unrecognizable under collecting or field conditions. In microscopic view, it is distinguished by its dark green color and co-occurrence with other minerals in CAI inclusions. ## Distinguishing from Similar Minerals Burnettite is visually similar to other pyroxenes found in CAI inclusions, such as diopside, hedenbergite, and esseneite. Definitive differentiation requires chemical composition analysis, especially confirmation of the dominance of trivalent vanadium (V³⁺) at one of the sites in the crystal structure. ## Crystal Forms Burnettite forms exclusively microscopic, anhedral grains, often with an irregular shape, occurring within mineral aggregates.

Geological environment

## Genesis Burnettite crystallizes under very specific conditions, at high temperatures and low pressure, as prevailed in the primordial solar nebula. It forms in calcium-aluminum-rich inclusions (CAIs) within carbonaceous chondrites. It is considered one of the earliest crystallizing silicates in the Solar System. ## Mineral Associations This mineral co-occurs with other minerals typical of CAI inclusions, such as spinel, melilite, anorthite, grossite, perovskite, and other pyroxenes (e.g., titanium diopside). ## Localities The only confirmed locality of burnettite is the Allende meteorite, which fell in Chihuahua, Mexico. It was found in a specific CAI inclusion within this meteorite.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, burnettite is not traded by collectors as isolated specimens. Its value is purely scientific. For research institutions and specialized meteorite collectors, the value lies in the Allende meteorite sample itself containing confirmed CAI inclusions with burnettite. The value of such a sample (usually in the form of a polished section) depends on its size, preparation quality, and scientific documentation confirming the presence of the mineral.

Care and storage

## Cleaning Specimens containing burnettite (usually in the form of thin polished sections from meteorites) should not be wet cleaned. Fine dust particles can be removed using compressed air or a very soft brush. ## What to Avoid Avoid contact with water, chemicals, ultrasound, and sudden temperature changes. Meteorites containing burnettite may include minerals sensitive to moisture and oxidation. ## Storage Samples with burnettite should be stored under stable conditions, preferably in a dry environment, e.g., in a box with a desiccant. They should be protected from dust and mechanical damage.

Sources

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