NWA 17707 Ordinary Chondrite Meteorite Slice, LL4, 27.61g, Preserved Chondrules

Full slice exposing ancient solar nebula material

This complete slice cuts through NWA 17707, exposing the internal structure of a primitive ordinary chondrite. Rounded chondrules stand out against the darker matrix material, representing droplets of molten rock that solidified in the solar nebula before planets formed. The slice format reveals the distribution and size variation of these spherical structures throughout the specimen, providing a window into the earliest stages of planetary formation. At 27.61g, this full slice captures a representative cross-section of the meteorite's internal composition.

The natural contrast between lighter chondrules and darker matrix creates visual depth across the polished surface. Individual chondrules range from sub-millimeter to several millimeters in diameter, each preserving a record of rapid cooling in the protoplanetary disk. The slice maintains structural integrity while revealing the meteorite's internal architecture.

Structure and features

The LL4 classification reflects two defining characteristics visible in this specimen. The LL designation indicates low total iron content (19-22% by mass) and low metallic iron, distinguishing this meteorite from the more iron-rich H and L ordinary chondrite groups. The type 4 petrologic grade indicates moderate thermal metamorphism—enough heat to alter some mineral structures while preserving the original chondrule boundaries. Chondrules remain distinct and easily visible rather than being integrated into a more homogeneous matrix that would characterize higher metamorphic grades.

The polished surface reveals olivine and pyroxene crystals within the chondrules, surrounded by fine-grained matrix material. Metal flakes appear as small bright inclusions distributed throughout the slice. The chondrule boundaries show clear delineation, a diagnostic feature of type 4 metamorphism that distinguishes this specimen from more heavily altered types 5 and 6.

Scientific context

NWA 17707 belongs to the ordinary chondrite group, the most abundant meteorite type in collections but each fall providing distinct scientific value. Ordinary chondrites formed in the asteroid belt between Mars and Jupiter approximately 4.567 billion years ago, predating Earth's formation. The LL group specifically derives from parent bodies with depleted iron content compared to other ordinary chondrites, suggesting formation in a different region of the protoplanetary disk where oxygen fugacity was higher.

The type 4 metamorphic grade indicates the parent asteroid experienced internal heating sufficient to reach temperatures between 600-700°C, likely from decay of short-lived radioactive isotopes like aluminum-26. This heating occurred within the first few million years after solar system formation. Despite this thermal processing, the original chondrule structures survived, making LL4 specimens valuable for studying both nebular condensation processes and early asteroid thermal evolution. Learn About Meteorites provides additional context on chondrite classification and formation.

Frequently asked questions

Is this meteorite authenticated? NWA 17707 is classified in the Meteoritical Bulletin as an LL4 ordinary chondrite. You can verify this classification through the Meteoritical Bulletin database. This specimen includes a certificate of authenticity documenting the classification, weight, and provenance.

What does LL4 classification mean? The first L indicates low total iron content (19-22% by weight). The second L indicates low metallic iron content specifically. The number 4 represents the petrologic type, showing the meteorite experienced moderate thermal metamorphism—enough heat to alter mineral chemistry while preserving visible chondrule boundaries. This distinguishes it from type 3 (unmetamorphosed) and types 5-6 (higher metamorphism with integrated chondrules).

What is included with this specimen? You receive the 27.61g full slice and a certificate of authenticity. The specimen does not include a display stand.

Why are chondrules scientifically significant? Chondrules are the oldest solid materials in the solar system, forming within the first few million years after the Sun ignited. They condensed directly from the solar nebula as molten droplets, then cooled rapidly before being incorporated into asteroids. Each chondrule preserves information about temperature, oxygen fugacity, and chemical conditions in the protoplanetary disk.

Collector significance

LL chondrites represent only 10-11% of ordinary chondrite falls, making them less common than H and L groups in collections. The type 4 metamorphic grade occupies a middle position in the petrologic sequence, showing more textural interest than highly metamorphosed types 5-6 while displaying more mineral equilibration than primitive type 3 specimens. This balance makes LL4 specimens particularly educational for understanding metamorphic progression in asteroid interiors.

The 2024 recovery date places NWA 17707 among recent Saharan finds, with classification completed and published within the past year. Full slices provide optimal display format for chondrites, revealing internal structure that remains hidden in exterior-only specimens. The weight falls in a range suitable for detailed examination while remaining accessible to collectors building comprehensive Ordinary Chondrite reference sets across the H, L, and LL groups.

Meteoritical Bulletin entry: NWA 17707 | Classification: Ordinary Chondrite (LL4) | Find, Algeria, 2024