{"title":"Primitive Achondrites","description":"\u003cp\u003ePrimitive achondrites sit between the chondrites and the fully igneous achondrites. Their parent bodies were heated enough to recrystallize and begin melting, but not enough to separate completely into core, mantle and crust, so these meteorites carry the interlocking crystalline texture of an achondrite while keeping a bulk composition close to that of a chondrite.\u003c\/p\u003e\n\u003cp\u003eThe named groups include the winonaites, the acapulcoites and lodranites, and material that remains ungrouped within the primitive achondrite class. Distinguishing between them relies on mineral chemistry, and the classifications published in the Meteoritical Bulletin state which measurements were used.\u003c\/p\u003e\n\u003cp\u003eEvery classified specimen here is listed with its Meteoritical Bulletin data. Where the Bulletin records a caveat about a classification, the listing states it.\u003c\/p\u003e","products":[{"product_id":"bir-ounane-001-achondrite-prim-ungrouped-slice-w-coa-6-46g-rare-1-of-16-classifications","title":"Bir Ounane 001 Achondrite-prim Meteorite Slice, Ungrouped, 6.46g, Polished Primitive Crust","description":"\u003ch2\u003ePrimitive achondrite from early planetary evolution\u003c\/h2\u003e\n\u003cp\u003eThis 6.46g polished slice captures material from the earliest stages of planetary differentiation. Bir Ounane 001 represents a transitional state between chondritic and fully differentiated material, preserving textures from incomplete melting and separation processes that occurred in the solar system's first million years. The polished surface reveals the fine-grained matrix and subtle mineral variations characteristic of primitive achondrites, offering direct evidence of how planetesimals evolved from undifferentiated rock into layered worlds.\u003c\/p\u003e\n\u003cp\u003eClassified as Achondrite-prim with no established group affiliation, this meteorite occupies a scientific middle ground. The specimen shows neither the chondrule-rich structure of primitive chondrites nor the clean crystalline texture of fully evolved achondrites. Instead, the slice displays a complex assemblage that records partial differentiation, the interrupted transformation of primordial material under thermal and gravitational forces.\u003c\/p\u003e\n\u003ch2\u003eStructure and features\u003c\/h2\u003e\n\u003cp\u003eThe polished surface exposes a fine-grained groundmass punctuated by mineralogical variations that reflect incomplete separation of silicate phases. Unlike the coarse crystals seen in eucrites or the metallic networks of differentiated bodies, this slice shows textural heterogeneity consistent with material that experienced heating sufficient to begin recrystallization but insufficient to complete planetary layering. Small-scale variations in reflectivity across the polish indicate compositional gradients frozen during early thermal processing.\u003c\/p\u003e\n\u003cp\u003eThe slice preparation emphasizes these subtle structural details. Polishing reveals mineral boundaries and melt features that would remain invisible in a natural state specimen. The thin profile allows transmitted light examination, though the opacity and fine grain size limit this technique compared to thinner petrographic sections.\u003c\/p\u003e\n\u003ch2\u003eScientific context\u003c\/h2\u003e\n\u003cp\u003ePrimitive achondrites represent a rare window into interrupted differentiation. While most meteorite parent bodies either remained completely primitive (chondrites) or differentiated fully into core-mantle-crust structures (producing irons, stony-irons, and evolved achondrites), a small population of bodies experienced intermediate thermal histories. Bir Ounane 001 belongs to this scientifically valuable category, showing evidence of metamorphism and partial melting without complete magmatic processing.\u003c\/p\u003e\n\u003cp\u003eThe ungrouped classification indicates this material does not match the chemical or isotopic signatures of established meteorite clans. Among approximately 75,000 classified meteorites, only sixteen carry the Achondrite-prim designation, placing Bir Ounane 001 within an exceptionally small statistical cohort. This scarcity reflects both the rarity of primitive achondrite parent bodies and the difficulty of recognizing these meteorites in the field, where their appearance can resemble terrestrial rocks. Collectors seeking comprehensive representation of meteorite diversity will find this classification essential, as it documents a transitional stage that most solar system bodies bypassed entirely. For broader meteorite classification context, see \u003ca href=\"\/pages\/learn-about-meteorites\"\u003eLearn About Meteorites\u003c\/a\u003e.\u003c\/p\u003e\n\u003ch2\u003eFrequently asked questions\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eIs this meteorite authenticated?\u003c\/strong\u003e Yes. Bir Ounane 001 is classified in the Meteoritical Bulletin as Achondrite-prim (ungrouped). You can verify this classification through the \u003ca href=\"https:\/\/www.lpi.usra.edu\/meteor\/metbull.php?sea=Bir%20Ounane%20001\u0026amp;sfor=names\" rel=\"noopener\" target=\"_blank\"\u003eMeteoritical Bulletin database\u003c\/a\u003e. This specimen includes a certificate of authenticity documenting its provenance and classification status.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat does Achondrite-prim mean?\u003c\/strong\u003e The designation indicates a primitive achondrite, a meteorite that experienced thermal processing beyond the chondritic state but did not undergo complete differentiation into distinct planetary layers. These meteorites preserve evidence of early, incomplete melting and recrystallization that occurred during planetesimal formation.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhy is this meteorite ungrouped?\u003c\/strong\u003e Ungrouped status means Bir Ounane 001's chemical and isotopic composition does not match any established meteorite group. This classification reflects either a unique parent body or insufficient material for comprehensive analysis. Ungrouped meteorites often represent small asteroids that contributed few specimens to Earth's meteorite collection.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is included with this specimen?\u003c\/strong\u003e You receive the 6.46g polished slice and a certificate of authenticity. No display stand is included unless separately confirmed.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow rare are primitive achondrites?\u003c\/strong\u003e Extremely rare. Only sixteen meteorites carry the Achondrite-prim classification among tens of thousands of classified falls and finds. This scarcity makes specimens from this group particularly valuable for comprehensive meteorite collections.\u003c\/p\u003e\n\u003ch2\u003eCollector significance\u003c\/h2\u003e\n\u003cp\u003eBir Ounane 001 addresses a specific gap in systematic meteorite collections. Most collectors accumulate representatives of common chondrite groups and familiar achondrites like eucrites and diogenites, but primitive achondrites receive disproportionately little attention despite their scientific importance. The sixteen-meteorite cohort means acquiring any Achondrite-prim specimen requires deliberate effort, these do not appear regularly in dealer inventories.\u003c\/p\u003e\n\u003cp\u003eThis 6.46g slice offers entry into primitive achondrite collecting at an accessible size. The polished preparation maximizes visibility of internal features while maintaining a specimen large enough for clear visual examination without magnification. For collectors building taxonomically complete collections, this piece fills a classification slot that may not appear again for months or years. Those focusing specifically on ungrouped meteorites or early differentiation processes will find this specimen directly relevant to both themes. Explore related differentiated specimens in our \u003ca href=\"\/collections\/ungrouped-achondrites\"\u003eUngrouped Achondrites\u003c\/a\u003e collection, or examine other primitive material in our \u003ca href=\"\/collections\/stony-meteorites\"\u003eStony Meteorites\u003c\/a\u003e collection.\u003c\/p\u003e\n\u003cp\u003eMeteoritical Bulletin entry: \u003ca href=\"https:\/\/www.lpi.usra.edu\/meteor\/metbull.php?sea=Bir%20Ounane%20001\u0026amp;sfor=names\" rel=\"noopener\" target=\"_blank\"\u003eBir Ounane 001\u003c\/a\u003e | Classification: Achondrite-prim | Find, Mali, 2022\u003c\/p\u003e","brand":"Treasure Coast Meteorite Co.","offers":[{"title":"Default Title","offer_id":44755658506287,"sku":"BIR-OUNANE-001-6.46G-SLICE","price":95.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0726\/9724\/9839\/files\/bir-ounane-001.png?v=1780155729"},{"product_id":"nwa-18593-winonaite-meteorite-end-cut-279-74g-mirror-polished","title":"NWA 18593 Winonaite Meteorite End Cut 279.74g Mirror Polished Primitive Achondrite","description":"\u003ch2\u003eA mirror polished end cut of a winonaite\u003c\/h2\u003e\n\u003cp\u003eNorthwest Africa 18593 is a winonaite, one of the primitive achondrites. These meteorites carry the recrystallized texture of an achondrite while keeping a bulk composition close to that of a chondrite, and they sample parent bodies that were heated to the point of partial melting early in the history of the solar system. This 279.74 g end cut has been mirror polished across its full cut face, where bright metallic grains are scattered through a dark silicate groundmass and change with every angle of the light.\u003c\/p\u003e\n\n\u003ch2\u003eStructure and features\u003c\/h2\u003e\n\u003cp\u003eThe cut face is mirror polished, not etched, and carries no coating. Under direct light it reads silver and bright; turned away from the light it goes dark, with the metallic grains picking out points of reflection across the whole surface. The Meteoritical Bulletin records Fe-Ni metal, troilite and chlorapatite as accessory phases in this meteorite.\u003c\/p\u003e\n\u003cp\u003eA network of fine fractures crosses the polished face, several of them with brown fill. The Bulletin records a moderate weathering grade and a moderate shock stage for NWA 18593, and the fractures are part of what this stone looks like after time in the desert. The reverse and edges keep the natural exterior, a knobby, weathered surface with light tan material in some of the recesses. The Bulletin describes the three stones as having weathered fusion crust.\u003c\/p\u003e\n\u003cp\u003eIn thin section, the Bulletin describes a granoblastic texture of olivine, low-Ca pyroxene, high-Ca pyroxene and plagioclase, with a mean silicate grain size of about 0.3 mm and grain boundaries often meeting at roughly 120 degree triple junctions. In parts of the section, rounded olivine is enclosed within larger poikiloblasts of low-Ca pyroxene. These are microscope observations from the classification section, not features visible on the polished face by eye.\u003c\/p\u003e\n\n\u003ch2\u003eDiscovery and provenance\u003c\/h2\u003e\n\u003cp\u003eAccording to the Meteoritical Bulletin, three stones were found in 2023 in Mauritania and were later purchased online in 2025 by Brian McDonald from a meteorite dealer in Morocco. The recorded total known weight is 1986 g across three pieces.\u003c\/p\u003e\n\u003cp\u003eMaterial was submitted by Daniel Sheikh and classified by D. Sheikh at the Cascadia Meteorite Laboratory, Portland State University, where the 29 g type specimen is held. The Bulletin records the main mass with Brian McDonald. The name was approved on 16 May 2026, and the meteorite is listed in Meteoritical Bulletin 115, which is in preparation and not yet a published volume. The Bulletin notes that information from MB 115 or later remains subject to change by the Meteorite Nomenclature Committee.\u003c\/p\u003e\n\u003cp\u003eThis end cut is not the main mass. It was cut from another of the three stones. Treasure Coast Meteorite Co. holds all recorded material of NWA 18593 apart from the type specimen at Cascadia.\u003c\/p\u003e\n\n\u003ch2\u003eScientific context\u003c\/h2\u003e\n\u003cp\u003ePrimitive achondrites include the acapulcoite and lodranite group and the winonaites, named for the Winona meteorite found in Arizona. Telling them apart has historically leaned on oxygen isotopes, which can overlap between groups. \u003ca href=\"https:\/\/doi.org\/10.1111\/maps.13944\" rel=\"noopener\" target=\"_blank\"\u003eStephant et al. (2023)\u003c\/a\u003e proposed separating them with three mineral measurements instead: the fayalite content of olivine, the FeO\/MnO ratio of olivine, and the potassium content of plagioclase. The same study defined a new related group, the tissemouminites.\u003c\/p\u003e\n\u003cp\u003eNWA 18593 was classified on that basis. Its olivine measures Fa4.3 with an FeO\/MnO ratio of 17, and its plagioclase is An21.7 Or3.5. The Bulletin states that the sample plots within the winonaite field on those three components, and that classification as a winonaite is favored over acapulcoite. That wording is carried here as the Bulletin gives it.\u003c\/p\u003e\n\u003cp\u003eFor more on how these groups fit into the wider picture, see \u003ca href=\"\/pages\/what-is-an-achondrite\"\u003ewhat is an achondrite\u003c\/a\u003e and \u003ca href=\"\/pages\/how-are-meteorites-classified\"\u003ehow meteorites are classified\u003c\/a\u003e.\u003c\/p\u003e\n\n\u003ch2\u003eFrequently asked questions\u003c\/h2\u003e\n\u003ch3\u003eIs NWA 18593 an officially classified meteorite?\u003c\/h3\u003e\n\u003cp\u003eYes. Northwest Africa 18593 is an official name in the Meteoritical Bulletin Database, approved on 16 May 2026 and listed in Meteoritical Bulletin 115, which is in preparation. \u003ca href=\"\/pages\/meteoritical-bulletin-explained\"\u003eUnderstanding the Meteoritical Bulletin\u003c\/a\u003e explains what that status means.\u003c\/p\u003e\n\u003ch3\u003eWhat is a winonaite?\u003c\/h3\u003e\n\u003cp\u003eA primitive achondrite: a meteorite with the recrystallized texture of an achondrite and a composition still close to a chondrite. Winonaites are one of the named groups of primitive achondrites, alongside the acapulcoites and lodranites.\u003c\/p\u003e\n\u003ch3\u003eHow many winonaites have been approved?\u003c\/h3\u003e\n\u003cp\u003eThe Meteoritical Bulletin lists 109 approved meteorites classified as winonaite as of September 2026. That is a count of database entries. Pieces of the same fall recovered separately can be listed under different names until pairing is established, so the number of distinct meteorites may be lower.\u003c\/p\u003e\n\u003ch3\u003eIs this piece the main mass?\u003c\/h3\u003e\n\u003cp\u003eNo. The Bulletin records the main mass of NWA 18593 with Brian McDonald, and this end cut was cut from a different stone of the three. Treasure Coast Meteorite Co. holds all recorded material apart from the 29 g type specimen at Cascadia.\u003c\/p\u003e\n\u003ch3\u003eIs the cut face etched or coated?\u003c\/h3\u003e\n\u003cp\u003eNeither. The face is mirror polished only. It has not been etched and has no coating or epoxy.\u003c\/p\u003e\n\u003ch3\u003eHow should I care for it?\u003c\/h3\u003e\n\u003cp\u003eKeep it dry and handle the polished face as little as possible. The stone contains iron-nickel metal and already shows weathering, so humidity is the main thing to avoid. \u003ca href=\"\/pages\/do-meteorites-rust\"\u003eDo meteorites rust\u003c\/a\u003e covers storage in more detail.\u003c\/p\u003e\n\u003ch3\u003eDoes it come with documentation?\u003c\/h3\u003e\n\u003cp\u003eYes. This specimen carries serial TC-00046 and has a permanent public \u003ca href=\"\/pages\/specimen-record-tc-00046\"\u003especimen record\u003c\/a\u003e with its weight and photographs. The record is a reference document, not a certificate of authenticity or an appraisal.\u003c\/p\u003e\n\u003ch3\u003eWho is selling this specimen?\u003c\/h3\u003e\n\u003cp\u003eTreasure Coast Meteorite Co., Hobe Sound, Florida, IMCA Member #3323.\u003c\/p\u003e\n\n\u003ch2\u003eCollector significance\u003c\/h2\u003e\n\u003cp\u003eAt 279.74 g, this end cut is about 14 percent of the recorded total known weight of NWA 18593. It comes from the holder of the main mass and of every other recorded piece, with the full chain from the Bulletin writeup to this listing documented.\u003c\/p\u003e\n\u003cp\u003eThe complete classification is available in the \u003ca href=\"https:\/\/www.lpi.usra.edu\/meteor\/metbull.cfm?code=87169\" rel=\"noopener\" target=\"_blank\"\u003eMeteoritical Bulletin Database entry for Northwest Africa 18593\u003c\/a\u003e. More stony material is listed in the \u003ca href=\"\/collections\/primitive-achondrites\"\u003eprimitive achondrite collection\u003c\/a\u003e. Treasure Coast Meteorite Co., IMCA Member #3323.\u003c\/p\u003e\n","brand":"Treasure Coast Meteorite Co.","offers":[{"title":"Default Title","offer_id":46217879126063,"sku":"NWA-18593-279.74G-ENDCUT","price":4755.58,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0726\/9724\/9839\/files\/nwa-18593-winonaite-279.74g-01-polished-face-hero.jpg?v=1789871984"}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0726\/9724\/9839\/collections\/nwa-18593-winonaite-279.74g-01-polished-face-hero.jpg?v=1789959450","url":"https:\/\/www.tcmeteorites.com\/collections\/primitive-achondrites.oembed","provider":"Treasure Coast Meteorite Co.","version":"1.0","type":"link"}