Ksar Ghilane 022 Ungrouped Achondrite Meteorite Slice, achondrite-ung, 2.33g, Augite-Dominated Matrix

Augite-rich specimen from an unclassified parent body

This 2.33-gram slice preserves a matrix dominated by equant augite crystals averaging 1.5 millimeters across, with subordinate enstatite and scattered accessory phases including chromian troilite, daubreelite, and alabandite. The rock crystallized from a melt on a differentiated asteroid whose identity remains unknown. Secondary calcite veining crosses the specimen, recording later aqueous alteration or terrestrial weathering. The texture and mineral assemblage set Ksar Ghilane 022 apart from established achondrite groups, making it a reference sample for comparative planetology.

Recovered in Tunisia in 2023, this material reached Earth after an unknown duration in space. The slice format exposes the internal structure, showing the crystalline fabric that formed as magma cooled within the crust or mantle of a small planetary body. No other meteorite shares this exact combination of pyroxene chemistry and accessory mineralogy, placing Ksar Ghilane 022 in a class by itself.

Pyroxene assemblage and accessory phases

Augite comprises the bulk of the specimen, with compositional ranges of Fs ~0.0–0.1 and Wo ~39.4–42.3. This calcium-rich pyroxene indicates crystallization from a basaltic melt at temperatures consistent with shallow magmatic environments. Enstatite grains, though minor, exhibit Fs ~0.1 and Wo ~0.9–3.6, suggesting localized variations in melt chemistry or later recrystallization.

Accessory sulfides include chromian troilite and daubreelite, both common in reduced igneous systems. Alabandite, a manganese sulfide, and an Mn-Fe oxide phase point to elevated manganese activity during crystallization. These phases typically form in oxygen-poor environments where sulfur and metal dominate over silicate melts. The calcite veins cutting the matrix formed after the rock solidified, likely during terrestrial residence or during a low-temperature aqueous event on the parent body.

Scientific context

Achondrites form when asteroid interiors melt and differentiate, separating metal cores from silicate mantles and crusts. Most achondrites fall into established groups linked to known parent bodies: eucrites and diogenites trace to asteroid 4 Vesta, angrites represent a distinct basaltic reservoir, and aubrites formed under extreme reduction. Ungrouped achondrites like Ksar Ghilane 022 document differentiation events on bodies that have not been sampled repeatedly or whose fragments have not survived in sufficient numbers to define a class.

The oxygen isotope data for Ksar Ghilane 022 do not match any known achondrite group, confirming its orphan status. This suggests the parent body either contributed few meteorites to Earth's collection or was geologically heterogeneous enough that individual samples vary widely. Understanding these outliers refines models of early solar system processes, particularly the diversity of melting and crystallization conditions across the asteroid belt. For further background on meteorite classification and formation, see Learn About Meteorites.

Frequently asked questions

Is this meteorite authenticated? Ksar Ghilane 022 is classified as achondrite-ung in the Meteoritical Bulletin Database. Each specimen ships with a certificate of authenticity from Treasure Coast Meteorite Co. You can verify the classification at Meteoritical Bulletin: Ksar Ghilane 022.

What does "ungrouped achondrite" mean? The classification indicates the meteorite formed through igneous differentiation on an asteroid but does not match the mineralogy, chemistry, or oxygen isotopes of any established achondrite group. It represents material from a parent body not yet linked to other known meteorites.

What is included with this specimen? The listing includes the 2.33-gram slice and a certificate of authenticity. No display stand is included unless separately noted.

Why is the parent body unknown? Most achondrite groups are defined by multiple falls or finds with shared characteristics. Ksar Ghilane 022 has a unique oxygen isotope signature and pyroxene assemblage, meaning no other meteorite has been found from the same source. This isolates it scientifically and increases its research value.

What are the secondary calcite veins? Calcite is a carbonate mineral that precipitates from water. The veins cutting this specimen likely formed on Earth after the meteorite fell, though some achondrites also show evidence of aqueous alteration on their parent bodies. The presence of calcite does not affect the primary igneous texture or classification.

Why collectors seek ungrouped achondrites

Ungrouped specimens represent fragments of asteroids that contributed few or no other samples to the terrestrial meteorite collection. Each one documents a unique thermal and chemical history, making them irreplaceable for comparative studies of planetary differentiation. Collectors value these meteorites for their scientific isolation and the questions they pose about the diversity of small-body geology.

This 2.33-gram slice balances portability with visual detail, preserving the augite-dominated matrix and accessory phases in a format suited to both display and close examination. The slice cut exposes the internal structure without requiring destructive sampling, making it accessible for educational or curatorial purposes. For additional ungrouped specimens and other differentiated materials, see the Ungrouped Achondrites collection.

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