Ksar Ghilane 022 Ungrouped Achondrite Meteorite End Cut, Achondrite-ung, 9.07g, Augite-Dominant Interior

Augite-rich igneous texture in a 9.07g end cut

This 9.07-gram end cut from Ksar Ghilane 022 exposes an interior dominated by coarse augite crystals that formed through differentiated melting processes. The slice reveals the mineral assemblage that distinguishes this ungrouped achondrite: predominantly equant augite grains averaging 1.5 millimeters across, interspersed with minor enstatite and accessory phases including chromium-bearing troilite, daubreelite, alabandite, and manganese-iron oxide. Secondary calcite veins crosscut the primary igneous texture.

The end cut format preserves one natural exterior surface while exposing a cross-section through the specimen's interior structure. The polished face allows direct observation of grain boundaries and the spatial relationships between augite, enstatite, and sulfide phases. This presentation makes the specimen particularly effective for examining the petrographic characteristics that place Ksar Ghilane 022 outside established achondrite classification schemes.

Mineral assemblage and crystallization history

The mineral chemistry recorded in the Meteoritical Bulletin confirms augite with ferrosilite content near 0.0 to 0.1 and wollastonite ranging from 39.4 to 42.3. Enstatite shows ferrosilite around 0.1 and wollastonite between 0.9 and 3.6. These compositions indicate crystallization from a magma that underwent significant fractionation, producing calcium-rich pyroxene as the dominant phase while retaining only minor orthopyroxene.

The accessory sulfide assemblage includes Cr-troilite, daubreelite, alabandite, and manganese-iron oxide, representing late-stage crystallization products. The presence of secondary calcite veins indicates post-crystallization alteration, likely during terrestrial weathering after the meteorite's fall to Earth. The combination of igneous minerals and terrestrial alteration features provides insight into both the specimen's formation environment and its history since arriving on our planet.

Scientific context

Ungrouped achondrites represent differentiated asteroidal material that cannot be assigned to known achondrite families. These meteorites formed through partial or complete melting of their parent bodies, producing igneous rocks with mineral assemblages distinct from both primitive chondrites and classified achondrite groups. Ksar Ghilane 022's augite-dominated composition, coupled with its specific pyroxene chemistry and accessory phases, sets it apart from eucrites, angrites, and other established achondrite classifications.

The specimen's oxygen isotope data places it outside the isotopic fields occupied by known achondrite groups, confirming its ungrouped status. This isotopic signature, combined with the unusual mineral assemblage, indicates formation on a differentiated asteroid with a distinct evolutionary history. Each ungrouped achondrite potentially represents material from a different parent body, making these specimens critical for understanding the diversity of igneous processes that occurred across the early Solar System. Collectors interested in differentiated meteorites can explore our complete selection at Ungrouped Achondrites.

Frequently asked questions

Is this meteorite authenticated? Ksar Ghilane 022 is officially classified in the Meteoritical Bulletin as Achondrite-ung. You can verify this classification at Meteoritical Bulletin Database. This specimen includes a certificate of authenticity from Treasure Coast Meteorite Co.

What does "ungrouped achondrite" mean? An ungrouped achondrite is a differentiated igneous meteorite that does not fit into any established achondrite classification scheme. The mineral assemblage, chemistry, and oxygen isotopes distinguish it from eucrites, diogenites, angrites, and other known groups, indicating it likely originates from a unique parent body.

What is included with this specimen? You receive the 9.07-gram end cut slice and a certificate of authenticity. No display stand is included with this specimen.

What are augite and enstatite? Augite and enstatite are both pyroxene minerals that form in igneous environments. Augite is a calcium-rich clinopyroxene that crystallizes at relatively high temperatures, while enstatite is a magnesium-rich orthopyroxene. The dominance of augite over enstatite in this specimen indicates the magma chemistry favored calcium-rich pyroxene during crystallization.

Why is the oxygen isotope composition significant? Oxygen isotope ratios act as a fingerprint for identifying parent bodies. Each asteroid or planetary body has a characteristic oxygen isotope signature that reflects conditions during its formation. Ksar Ghilane 022's oxygen isotopes fall outside the ranges occupied by known achondrite groups, providing strong evidence that it formed on a previously unsampled differentiated asteroid.

Display and collection value

The 9.07-gram size provides substantial hand specimen presence while remaining accessible for collectors building comprehensive achondrite collections. The end cut format offers both an exterior surface and a polished cross-section, allowing examination of both weathering features and internal structure. The coarse grain size makes individual augite crystals easily visible, providing a clear demonstration of the igneous texture that characterizes differentiated asteroidal material.

Ungrouped achondrites hold particular significance for collectors focused on parent body diversity. While classified achondrites like eucrites and angrites are well-represented in collections, ungrouped specimens offer the opportunity to own material from asteroids not otherwise represented in meteorite collections. This specimen documents a distinct differentiation history, mineral chemistry, and oxygen isotope signature that together define a separate lineage among differentiated Solar System bodies.

Meteoritical Bulletin entry: Ksar Ghilane 022 | Classification: Achondrite-ung | Find, Tunisia, 2023