NWA 18118 Oriented H5 Ordinary Chondrite, 644g Main Mass Individual

NWA 18118, an oriented H5 main mass

NWA 18118 is an officially classified H5 ordinary chondrite from Northwest Africa, offered here as a 644 gram oriented main mass individual. The total known weight recorded in the Meteoritical Bulletin is 682 grams, so this single stone accounts for the large majority of all documented material for NWA 18118. It is offered uncoated and substantially complete, with only a small classification window removed for analysis.

Structure and surface features

The stone shows a domed, shield-like profile consistent with an oriented flight position, in which a single leading face was held forward as the meteorite descended through the atmosphere. The exterior shows tones of brown and gray, with contoured surface relief and light desert patina from its time on the ground. A small area of caliche, a natural carbonate deposit picked up in the field, is present on one surface. The classification window exposes a fresh interior, where metal grains are visible as bright flecks alongside scattered chondrules set in a tan to gray matrix. Minor brown oxidation staining is present in the interior, as is typical of a desert find.

Discovery and provenance

NWA 18118 was recovered in Morocco and entered the scientific record with its classification published in the Meteoritical Bulletin, database entry 114, with a recovery year of 2024. The specimen carries a painted collection number on its reverse, consistent with documented Northwest African field material. It is offered with Treasure Coast Meteorite Co. provenance and the classification details noted below.

Scientific context, the H5 ordinary chondrite

Ordinary chondrites are the most abundant class of meteorite, and the H group is defined by high total iron content, a significant portion of it present as free metal. The petrologic type 5 indicates thermal metamorphism within the parent asteroid that partially equilibrated the original chondritic material while leaving chondrules still discernible. NWA 18118 was classified as H5 by magnetic susceptibility measurement. The Meteoritical Bulletin notes that this classification carries larger than normal uncertainty, which we state plainly here in the interest of full transparency. The official type of record remains H5.

Frequently asked questions

Is NWA 18118 officially classified?
Yes. It is an officially classified H5 ordinary chondrite recorded in the Meteoritical Bulletin, entry 114.

What does oriented mean?
An oriented meteorite held a stable position during atmospheric flight, ablating preferentially on its leading face and developing a directional, often domed or conical, shape. Oriented stones are sought after by collectors for that flight history.

Is this the complete known mass?
The total known weight on record is 682 grams. This specimen is the 644 gram main mass, with the balance accounted for by the classification sample and cutting loss.

Has the stone been coated or treated?
No. It is offered in natural condition, with no epoxy or stabilizing coating.

Collector significance

Owning the main mass of a classified meteorite places the single most significant piece of that find into one collection. At 644 grams against a 682 gram total known weight, NWA 18118 brings together main mass status, an oriented flight form, and an official H5 classification in one specimen. The full classification can be reviewed in the Meteoritical Bulletin entry for NWA 18118. Treasure Coast Meteorite Co., IMCA #3323.