{"product_id":"nwa-18592-mesosiderite-meteorite-main-mass-stony-iron-687-00g-largest-stone","title":"NWA 18592 Mesosiderite Meteorite Main Mass, Stony-Iron, 687.00g, Largest Stone","description":"\u003ch2\u003eThe main mass of NWA 18592, a mesosiderite stony-iron meteorite, at 687.00 grams\u003c\/h2\u003e\n\u003cp\u003eNWA 18592 is a mesosiderite, one of the two classes of \u003ca href=\"\/de\/collections\/stony-iron-meteorites\"\u003estony-iron meteorites\u003c\/a\u003e, built from metal and silicate rock broken and mixed together in roughly equal parts. The Meteoritical Bulletin records eleven stones and a total recorded mass of 903 grams, and lists the main mass with Brian McDonald. This 687.00 gram stone is the largest of the eleven and is that main mass.\u003c\/p\u003e\n\u003cp\u003eThe stone is dark brown to black across its exterior, lumpy and blocky, and crossed by a network of fine cracks. Pale tan desert sediment and small rounded sand grains are packed into many of those cracks and hollows. It was classified by D. Sheikh at Cascadia Meteorite Laboratory and approved in May 2026.\u003c\/p\u003e\n\u003ch2\u003eStructure and features\u003c\/h2\u003e\n\u003cp\u003eEvery surface shown in the photographs is natural exterior, with no saw cut and no polished face. The exterior breaks into rounded, knobby blocks separated by thin cracks, a pattern that shows on every side of the stone. Orange and rust brown staining runs along the cracks and across the lighter areas. The stone carries no coating.\u003c\/p\u003e\n\u003cp\u003eThe Bulletin describes the stones as having visibly weathered metal, and the classification section shows why. The metal portion, kamacite and taenite, is almost entirely replaced by iron hydroxide formed by weathering on Earth. That replacement accounts for the dark, rust toned exterior. The Bulletin records the shock stage as moderate and the weathering grade as moderate.\u003c\/p\u003e\n\u003cp\u003eIn thin section the sample is brecciated, made of broken fragments, with metal and silicate in roughly subequal proportions. The silicate portion is mostly low-calcium pyroxene, in clasts up to 1 mm that sometimes hold inclusions of high-calcium pyroxene, with lesser plagioclase. Silica, merrillite, troilite and chromite are present as accessory minerals.\u003c\/p\u003e\n\u003ch2\u003eDiscovery and provenance\u003c\/h2\u003e\n\u003cp\u003eNWA 18592 carries a Northwest Africa name, used for meteorites from the region whose exact find site is not documented. According to the Bulletin writeup, eleven stones were found in northwest Africa in 2024 and were purchased in 2025 by Brian McDonald online from a meteorite dealer in Morocco. Coordinates are recorded as unknown. More on how these names work is in \u003ca href=\"\/de\/pages\/nwa-meteorites-explained\"\u003eNWA meteorites explained\u003c\/a\u003e.\u003c\/p\u003e\n\u003cp\u003eThe meteorite was submitted by Daniel Sheikh, and D. Sheikh at Cascadia Meteorite Laboratory, Portland State University, carried out the petrography and classification. A 24.6 gram type specimen is held at Cascadia. The entry was approved on 16 May 2026 and is listed for Meteoritical Bulletin 115, which is in preparation and not yet a published volume.\u003c\/p\u003e\n\u003cp\u003eThe Bulletin records the main mass of NWA 18592 with Brian McDonald. Identification of this 687.00 gram stone as that main mass comes from Treasure Coast Meteorite Co. records. The recorded mass of 903 grams covers all eleven stones together and is not the weight of this stone.\u003c\/p\u003e\n\u003ch2\u003eScientific context\u003c\/h2\u003e\n\u003cp\u003eMesosiderites pair a silicate component that looks like crustal basalt and gabbro with iron-nickel metal, mixed together at high temperature and then broken and recombined. The silicate chemistry of NWA 18592 shows that crustal character. Low-calcium pyroxene averages Fs33.8 Wo3.7, high-calcium pyroxene averages Fs18.4 Wo38.5, and the plagioclase is highly calcic at An94.6. Those minerals are the same ones that make up the howardite, eucrite and diogenite meteorites, covered in the \u003ca href=\"\/de\/collections\/hed-meteorites\"\u003eHED meteorites\u003c\/a\u003e collection.\u003c\/p\u003e\n\u003cp\u003eThe other stony-iron class, the \u003ca href=\"\/de\/pages\/what-is-a-pallasite\"\u003epallasites\u003c\/a\u003e, pairs metal with olivine crystals instead. The two classes share a broad grouping by composition, not an origin. How meteorites are sorted into these classes is set out in \u003ca href=\"\/de\/pages\/how-are-meteorites-classified\"\u003ehow meteorites are classified\u003c\/a\u003e.\u003c\/p\u003e\n\u003ch2\u003eWhat the research reports\u003c\/h2\u003e\n\u003cp\u003eThe Meteoritical Bulletin classifies NWA 18592 as Mesosiderite, with no subgroup assigned. No published study of NWA 18592 itself is known beyond the Bulletin writeup. The study below concerns mesosiderites as a class and is included for the origin question it addresses. Its findings come from the authors' own samples and methods and are given as the study states them.\u003c\/p\u003e\n\u003ch3\u003eHaba, Wotzlaw, Lai, Yamaguchi and Schonbachler (2019)\u003c\/h3\u003e\n\u003cp\u003eM. K. Haba, J.-F. Wotzlaw, Y.-J. Lai, A. Yamaguchi and M. Schonbachler, \u003ca href=\"https:\/\/doi.org\/10.1038\/s41561-019-0377-8\" rel=\"noopener\" target=\"_blank\"\u003eMesosiderite formation on asteroid 4 Vesta by a hit-and-run collision\u003c\/a\u003e, Nature Geoscience (2019).\u003c\/p\u003e\n\u003cp\u003eThe authors dated zircon grains from mesosiderites by uranium-lead methods and found two ages: about 4,558.5 million years for formation of the original crust, and about 4,525.4 million years for the mixing of metal and silicate. Both ages line up with events recorded in the eucrite parent body, which they identify as probably the asteroid Vesta. In their words, \"This chronological coincidence corroborates that Vesta is the parent body of mesosiderite silicates.\" They propose that the mixing came from a hit-and-run collision with a smaller body. That model is the authors' hypothesis; the origin of mesosiderites is still debated, and the Bulletin does not assign a parent body.\u003c\/p\u003e\n\u003ch2\u003eFrequently asked questions\u003c\/h2\u003e\n\u003ch3\u003eIs this the main mass of NWA 18592?\u003c\/h3\u003e\n\u003cp\u003eThe Meteoritical Bulletin records the main mass of NWA 18592 with Brian McDonald. This 687.00 gram stone is the largest of the eleven stones and is that main mass, per Treasure Coast Meteorite Co. records.\u003c\/p\u003e\n\u003ch3\u003eIs the 903 gram figure the weight of this stone?\u003c\/h3\u003e\n\u003cp\u003eNo. 903 grams is the recorded mass for the meteorite as a whole, across eleven stones. This stone weighs 687.00 grams.\u003c\/p\u003e\n\u003ch3\u003eHas this stone been cut or polished?\u003c\/h3\u003e\n\u003cp\u003eNo saw cut or polished face shows anywhere on the stone. Every surface in the photographs is natural exterior.\u003c\/p\u003e\n\u003ch3\u003eWhy is the stone so dark and rusty?\u003c\/h3\u003e\n\u003cp\u003eThe metal in NWA 18592 has been almost entirely replaced by iron hydroxide through weathering on Earth, as the Bulletin records. That weathered metal gives the exterior its dark brown, black and rust tones. Background on how metal in meteorites weathers is in \u003ca href=\"\/de\/pages\/do-meteorites-rust\"\u003edo meteorites rust\u003c\/a\u003e.\u003c\/p\u003e\n\u003ch3\u003eWhat is in the cracks on the surface?\u003c\/h3\u003e\n\u003cp\u003ePale tan desert sediment and small rounded sand grains, lodged in the cracks and hollows of the exterior. They have been left in place.\u003c\/p\u003e\n\u003ch3\u003eWhat is a mesosiderite?\u003c\/h3\u003e\n\u003cp\u003eA stony-iron meteorite made of iron-nickel metal and silicate rock, broken and mixed together. The silicate part resembles the crust of a differentiated asteroid. Mesosiderites and pallasites are the two stony-iron classes.\u003c\/p\u003e\n\u003ch3\u003eHas NWA 18592 been published?\u003c\/h3\u003e\n\u003cp\u003eThe entry was approved on 16 May 2026 and is listed for Meteoritical Bulletin 115, which is in preparation. The classification is official; the volume is not yet published.\u003c\/p\u003e\n\u003ch3\u003eHow do I verify this is the same specimen shown in these photographs?\u003c\/h3\u003e\n\u003cp\u003eThis stone is recorded under serial \u003cstrong\u003eTC-00056\u003c\/strong\u003e. Its \u003ca href=\"\/de\/pages\/specimen-record-tc-00056\"\u003especimen record\u003c\/a\u003e is a permanent page holding the classification data as recorded in the Meteoritical Bulletin, the recorded weight, and photographs of this exact stone. Meteorite surfaces are individual to each stone, so a specimen in hand can be compared against those photographs and weighed against the recorded figure.\u003c\/p\u003e\n\u003ch3\u003eWho is the seller?\u003c\/h3\u003e\n\u003cp\u003eTreasure Coast Meteorite Co., IMCA Member #3323, Hobe Sound, Florida. Background on the Bulletin and what its entries record is in \u003ca href=\"\/de\/pages\/meteoritical-bulletin-explained\"\u003eunderstanding the Meteoritical Bulletin\u003c\/a\u003e.\u003c\/p\u003e\n\u003ch2\u003eCollector significance\u003c\/h2\u003e\n\u003cp\u003eThis is the main mass of an officially classified mesosiderite, the largest of its eleven stones, and it holds about three quarters of the meteorite's recorded mass. It is offered with its natural exterior as it was received.\u003c\/p\u003e\n\u003cp\u003eAs of November 2026, the Meteoritical Bulletin lists NWA 18592 as 1 of 306 approved meteorites classified as Mesosiderite.\u003c\/p\u003e\n\u003cp\u003eThis specimen is offered by Treasure Coast Meteorite Co., IMCA Member #3323, and is issued with a permanent specimen record and serial number, listed in the \u003ca href=\"\/de\/pages\/specimen-registry\"\u003eSpecimen Registry\u003c\/a\u003e. Browse more \u003ca href=\"\/de\/collections\/stony-iron-meteorites\"\u003estony-iron meteorites\u003c\/a\u003e in the collection.\u003c\/p\u003e\n\u003cp\u003eClassification and provenance for this specimen follow the official Meteoritical Bulletin entry for NWA 18592, viewable at the \u003ca href=\"https:\/\/www.lpi.usra.edu\/meteor\/metbull.cfm?code=87168\" rel=\"noopener\" target=\"_blank\"\u003eMeteoritical Bulletin Database\u003c\/a\u003e.\u003c\/p\u003e","brand":"Treasure Coast Meteorite Co.","offers":[{"title":"Default Title","offer_id":47138483208239,"sku":"NWA-18592-687.00G-MAIN-MASS","price":3091.5,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0726\/9724\/9839\/files\/nwa-18592-mesosiderite-687g-main-mass-side-view.jpg?v=1794030359","url":"https:\/\/www.tcmeteorites.com\/de\/products\/nwa-18592-mesosiderite-meteorite-main-mass-stony-iron-687-00g-largest-stone","provider":"Treasure Coast Meteorite Co.","version":"1.0","type":"link"}