NWA 17916 CO3 Carbonaceous Chondrite Meteorite End Cut, Main Mass with Fusion Crust, 320.79g

NWA 17916 CO3 carbonaceous chondrite end cut, 320.79 grams

This end cut weighs 320.79 grams and is the largest piece of NWA 17916 held by Treasure Coast Meteorite Co. A CO3 carbonaceous chondrite found in 2025 in Tindouf, Algeria, it presents one large cut face across the interior, with the remainder of the stone retaining its original exterior surface and fusion crust. Pale caliche remains on parts of the crust. The field number BMD 016 is painted on the exterior, the working name under which this meteorite was submitted for classification.

Structure and features

The cut face exposes a full interior section of the stone and carries a dense population of chondrules through a fine grained matrix. The Meteoritical Bulletin records a mean chondrule diameter of 247 plus or minus 116 micrometres across 36 measured examples, with clear boundaries and minimal alteration at the margins. The textural types identified in thin section include porphyritic olivine, barred olivine and radial pyroxene. At this scale the cut face shows the chondrule population across a far larger area than a slice can, along with several darker inclusions set into the matrix.

Calcium-aluminium-rich inclusions are present in this meteorite, averaging 332 plus or minus 102 micrometres across 34 measured examples, with sharp outlines and fine grained high temperature mineral phases. CAIs are the oldest dated solids in the solar system, and their presence is one of the features that separates carbonaceous chondrites from the ordinary chondrite groups. The opaque component of the matrix is dominated by troilite and magnetite, occurring as dispersed grains and as interstitial filling between silicate components.

The exterior retains fusion crust across a substantial part of the surface, formed as the outer skin of the stone melted during its passage through the atmosphere. Shallow depressions across the crust are regmaglypts, sculpted by the airflow during descent. The Bulletin records the recovered stones as brown in colour with desert varnished fusion crust, and the crust here carries that varnish. Separately, pale tan caliche adheres to sections of the crust. Caliche is a calcium carbonate deposit that forms around stones lying in arid soils and is common on meteorites recovered from the Sahara. It sits on the exterior of the stone rather than being part of the meteorite, and it has been left in place.

Across the cut face the matrix carries brown and orange colouration. The Bulletin records the weathering grade for NWA 17916 as low and notes that no significant weathering products were observed in thin section, indicating minimal terrestrial alteration.

Discovery and provenance

NWA 17916 was found in 2025 as two stones with a combined total known weight of 742.17 grams, brown in colour with desert varnished fusion crust. The find location is recorded as Tindouf, Algeria, the place of purchase as Morocco, and the finder as anonymous. The Bulletin records that the meteorite was purchased from a meteorite dealer.

Classification was performed by J. Garcia, ADARA, in the Canary Islands, Spain. The type specimen of 20.35 grams is held by MUNA, the Museo de la Naturaleza y Arqueologia in Santa Cruz de Tenerife, Spain, with three thin sections retained at ADARA. Classification was approved 14 September 2025 and published in Meteoritical Bulletin 114, Meteoritics and Planetary Science volume 61, pages 942 to 946. The CO3 designation rests on mineral composition, magnetic susceptibility of 4.39, and chondrule diameter.

The Bulletin records the main mass as being with Brian McDonald, and the working name as BMD 016. The identification of this particular end cut as that mass is made by Treasure Coast Meteorite Co. and is not stated by the Bulletin. The slices of NWA 17916 offered separately were cut from this stone.

Scientific context

CO chondrites take their group name from Ornans, the French fall that defines the type. The group is distinguished by chondrules that are small by the standards of chondritic meteorites, set in a matrix that makes up a modest fraction of the rock by volume. That combination is what produces the densely packed appearance on a cut face.

The petrologic type 3 designation records that the material escaped significant thermal processing on its parent body. Chondrules retain their original textures and boundaries rather than having been recrystallised, and compositional differences between individual chondrules survive. Olivine composition in NWA 17916 is recorded at Fa 18.2 plus or minus 11.1, and the width of that spread is itself a marker of a type 3 assemblage, since thermal metamorphism drives such compositions toward a single equilibrated value. Further specimens are held in the Carbonaceous Chondrites collection and the broader Chondrites collection.

Frequently asked questions

What does the CO3 classification mean?
CO identifies the Ornans group of carbonaceous chondrites. The 3 is the petrologic type and indicates that the material has not undergone significant thermal alteration on its parent body.

What is an end cut?
An end cut is the portion of a stone that remains after slices have been removed from one side. It presents a single large cut face while keeping the original exterior across the rest of the specimen, so both the interior and the crust can be seen on one piece.

What are the shallow depressions on the crust?
Regmaglypts. They are shaped by airflow across the softened surface of the stone during atmospheric entry, and are a feature of the meteorite itself rather than damage or terrestrial wear.

What is the pale material on the crust?
Caliche, a calcium carbonate deposit that forms around stones lying in arid soils. It is terrestrial material sitting on the outside of the stone, not part of the meteorite. It can be removed, and it has been left in place here.

What is the BMD 016 marking?
It is the field number under which this meteorite was submitted for classification, recorded in the Meteoritical Bulletin entry as the working name. It ties the physical stone to the published record.

What does NWA mean in the name?
NWA stands for Northwest Africa and is applied to meteorites recovered from that region without a precisely documented find site. The number that follows is a sequential identifier assigned on classification. Our guide to NWA meteorite designations covers this in full.

How can I verify the classification independently?
The Meteoritical Bulletin Database is public and free to search. Our page on understanding the Meteoritical Bulletin explains how to read an entry field by field.

Collector significance

An end cut of this size does something neither a slice nor a complete individual can. It shows the full interior section and the original crusted exterior on the same specimen, so the chondrule population, the regmaglypts and the desert varnish are all present in one piece. At 320.79 grams it is a substantial fraction of a meteorite whose total known weight the Meteoritical Bulletin records as 742.17 grams across two stones. As recorded in the Meteoritical Bulletin database in August 2026, NWA 17916 is one of 686 approved meteorites classified as CO3.

This specimen carries serial TC-00036 in the Treasure Coast Meteorite Co. specimen register, with a permanent record page documenting its identification, classification data and photographs. The full Bulletin entry, including petrographic data, geochemistry, type specimen holding and approval date, can be read at the Meteoritical Bulletin Database entry for Northwest Africa 17916.