NWA 17916 CO3 Carbonaceous Chondrite Meteorite Slice, 13.67g, Dense Chondrule Population

Chondrule density in primitive matrix

This 13.67-gram slice reveals the characteristic structure of CO3 carbonaceous chondrites: small, tightly packed chondrules suspended in a fine-grained matrix. The slice format provides direct visual access to dozens of individual chondrules, each representing a discrete melting event in the solar nebula. The dark matrix material contains the same volatile-rich compounds and presolar grains that make CO chondrites essential to understanding early solar system chemistry.

The slice measures substantial enough for detailed examination while remaining accessible for collectors building primitive meteorite reference collections. Surface preparation reveals chondrule boundaries and matrix texture without obscuring the specimen's natural composition.

Structure and features

CO chondrites derive their designation from the type specimen that fell in Ornans, France in 1868. This group exhibits the smallest average chondrule size among ordinary chondrites, typically 150 micrometers in diameter, creating the dense packing visible throughout this slice. The Type 3 petrologic grade confirms minimal thermal alteration since accretion, meaning the minerals and organic compounds present retain their original nebular states.

Refractory calcium-aluminum-rich inclusions (CAIs) appear as lighter-toned irregular shapes within the matrix. These inclusions formed at temperatures exceeding 1,300 degrees Celsius in the innermost regions of the protoplanetary disk before being transported outward and incorporated into the parent asteroid. The matrix itself contains phyllosilicates, magnetite, and organic compounds that formed at much lower temperatures, demonstrating the heterogeneous mixing that characterized the early solar nebula.

Discovery and provenance

NWA 17916 was recovered in 2025 as two stones totaling 742.17 grams in the Tindouf region of Algeria. The specimens display brown coloration with desert varnished fusion crust, consistent with extended terrestrial residence in arid conditions while remaining fresh enough to preserve primitive carbonaceous chondrite features.

Classification was performed by Jose Garcia of ADARA (Petrography and Curation of Astromaterials, Canary Islands, Spain). The type specimen of 20.35 grams is held by MUNA (Museo de la Naturaleza y Arqueologia, Tenerife, Spain), with three thin sections retained at ADARA. The main mass is held by Brian McDonald of Treasure Coast Meteorite Co. The classification was approved 14 September 2025 and published in Meteoritical Bulletin 114.

Petrographic analysis confirmed the CO3 designation through mineral composition, magnetic susceptibility (4.39), and chondrule diameter measurements. Mean chondrule diameter is 247 plus or minus 116 micrometers across 36 measurements, with CAIs averaging 332 plus or minus 102 micrometers. Olivine compositions of Fa 18.2 and low-calcium pyroxene of Fs 4.7 fall within the established CO3 range, and weathering is graded low.

Scientific context

CO chondrites formed in the outer asteroid belt approximately 4.567 billion years ago, capturing a mixture of high-temperature condensates and low-temperature ices and organics. The parent body accreted quickly enough to avoid significant heating from radioactive decay, preserving the primitive composition. This makes CO3 specimens like NWA 17916 critical for understanding the chemical and isotopic inventory available during planet formation.

Studies of CO chondrites have identified presolar silicon carbide and graphite grains, literal stardust older than the solar system itself, embedded in the matrix. The organic compounds include amino acids and other prebiotic molecules, supporting the hypothesis that carbonaceous chondrites delivered the chemical building blocks of life to the early Earth.

Frequently asked questions

Is this meteorite authenticated? Yes. NWA 17916 is classified as CO3 in the Meteoritical Bulletin. The official classification record is publicly available through the Meteoritical Society database.

What makes CO chondrites special? CO chondrites preserve the most primitive material from the early solar system, including presolar grains, CAIs, and organic compounds. Their small, tightly packed chondrules and abundant inclusions make them especially valued by researchers and collectors.

How rare is this classification? CO chondrites represent approximately 1 percent of all observed meteorite falls, making them considerably less common than ordinary chondrites in both research collections and the private market.

How was the slice prepared? The specimen was cut using a precision diamond saw and the cut surface was polished to reveal the internal chondrule and matrix structure. This preparation allows direct visual examination without obscuring the primitive composition.

Is shipping insured? Yes. All specimens ship fully insured with tracking. Treasure Coast Meteorite Co. handles each piece with care appropriate to its scientific and collector value.

Collector significance

CO chondrites represent approximately 1 percent of observed meteorite falls, making them considerably less common than ordinary chondrites in collections. The combination of small chondrule size, abundant CAIs, and preserved organics makes them particularly valued by institutions and private collectors focused on early solar system materials. This 13.67-gram slice provides sufficient size for both display and comparative study without the investment required for larger specimens.

The piece displays well from either side, allowing collectors to showcase the chondrule population regardless of orientation. The slice format offers more accessible pricing than complete individuals while preserving the full scientific characteristics that define the group. Explore additional primitive specimens in our Carbonaceous Chondrites collection.

Meteoritical Bulletin entry: Northwest Africa 17916. 742.17 g | MB 114 (2025).