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24.04g Eucrite Monomict with fusion crust I HED achondrite I NWA 12928
Top Meteorite
- $343.00
On Offer: 24.04 gram partially fusion crustedEucrite Monomict HED achondrite with official name Northwest Africa 12928
Dimensions: 34.30 mm x 30.15 mm x 20.50 mm
Official name: Northwest Africa 12928
Abbreviation: NWA 12928
Type: Eucrite, Monomict Basaltic Breccia
Origin: Northwest Africa
Description: 24.04 gram fragment of achondrite eucrite monomict, NWA 12928 with some crust, interior reveals a fragmental breccia of lithic clasts set in a light colored, fine-grained groundmass.
The HED Meteorite Clan: petrological evidence and data from NASA's Dawn mission indicate that nearly monomineralic ultramafic orthopyroxenite, olivine-bearing, and the much more rare harzburgitic, and dunite diogenites formed alongside each other. They likely originated as cumulates within localized magma chambers (plutons) situated across Vesta's lower crust and the lower-crust/upper-mantle transition zone. While the eucrites represent more evolved plagioclase rich mafic upper to middle zone crustal material. The howardites were formed by impact mixing, both in situ and during ejection events, of the diogenitic and eucritic material.
The HED meteorites are so named for the three types of meteorites that comprise the group; Howardite, Eucrite and Diogenite. The Eucrite and Diogenite are meteorites with distinct chemistries, while the Howardite is a mix of the eucritic and diogenitic material. The HEDs are differentiated achondritic meteorites, thought to originate from the large differentiated asteroid 4 Vesta. Vesta is one of the only asteroids visible with the naked eye and low powered telescopes. The Vesta parent body origin for the HED clan of meteorites is considered to have been conclusively established for many years. However, the late Dr. John Wasson, a planetary science researcher from UCLA had long held that the HED meteorite clan originated from another unknown Vesta-like asteroid that was blown apart long ago. This is because we also find a class of iron meteorites with nearly identical oxygen isotopes as the HED clan. This along with other research lead Dr. Wasson to conclude the HED clan of meteorites come from another differentiated V-type asteroid that was in a cataclysmic collision liberating part or all of its metal core along with the HED meteorites.
The HED meteorites are so named for the three types of meteorites that comprise the group; Howardite, Eucrite and Diogenite. The Eucrite and Diogenite are meteorites with distinct chemistries, while the Howardite is a mix of the eucritic and diogenitic material. The HEDs are differentiated achondritic meteorites, thought to originate from the large differentiated asteroid 4 Vesta. Vesta is one of the only asteroids visible with the naked eye and low powered telescopes. The Vesta parent body origin for the HED clan of meteorites is considered to have been conclusively established for many years. However, the late Dr. John Wasson, a planetary science researcher from UCLA had long held that the HED meteorite clan originated from another unknown Vesta-like asteroid that was blown apart long ago. This is because we also find a class of iron meteorites with nearly identical oxygen isotopes as the HED clan. This along with other research lead Dr. Wasson to conclude the HED clan of meteorites come from another differentiated V-type asteroid that was in a cataclysmic collision liberating part or all of its metal core along with the HED meteorites.
However, this hypothesis does not necessarily rule out the possibility that a "reaccreted" Vesta and the smaller V-type asteroids collectively known as Vestoids along with the HED meteorites and the isotopically paired irons were all once part of a much larger dwarf planet prior to a massive collision with another large body. While most researchers consider the case mostly closed on this debate, the paradox of isotopically paired core metal raised by Dr. Wasson's hypothesis has not been resolved. This leaves some to speculate that perhaps we still have more to learn about this fascinating clan of achondrite meteorites and even Vesta itself.
What you get: 24.04 gram NWA 12928 Eucrite meteorite specimen as shown, membrane storage box, and signed Certificate of Authenticity.
We offer a 100% no questions asked 30 day return policy.
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Northwest Africa 12928
Status: Official
| Basic information |
Name: Northwest Africa 12928 This is an OFFICIAL meteorite name. Abbreviation: NWA 12928 Observed fall: No Year found: 2016 Country: (Northwest Africa) Mass: 1530 g |
|---|---|
| Classification history: |
Meteoritical Bulletin, MB 108 (2020): Eucrite-mmict |
| Comments: | Approved 21 Nov 2019 |
| Writeup | Writeup from MB 108: Northwest Africa 12928 (NWA 12928) (Northwest Africa) Purchased: 2016 Classification: HED achondrite (Eucrite, monomict) History: Purchased Nov 2016 by Dustin Dickens in Mauritania from anonymous dealer. Physical characteristics: Single stone, fusion crusted exterior, saw cut reveals a fragmental breccia of lithic clasts set in a light colored, fine-grained groundmass. Petrography: (C. Agee, UNM) Microprobe examination of a polished mount shows approximately 60% pyroxene and 35% plagioclase. Many pyroxenes have exsolution lamellae. Minor silica and troilite observed. Geochemistry: (C. Agee, UNM) Low-Ca pyroxene Fs53.4±4.6Wo2.5±1.1, Fe/Mn=33±1, n=10; high-Ca pyroxene Fs37.6±17.0Wo28.8±21.7, Fe/Mn=31±2, n=2; plagioclase An80.5±12.3, n=6. Classification: Monomict basaltic eucrite, equilibrated. Specimens: 20.9 g including a probe mount on deposit at UNM, Dustin Dickens holds the main mass. |
| Data from: MB108 Table 0 Line 0: |
Place of purchase: Mauritania Date: P 2016 Mass (g): 1530 Pieces: 1 Class: Eucrite-mmict Shock stage: high Weathering grade: low Ferrosilite (mol%): 53.4±4.6, 37.6±17.0 Wollastonite (mol%): 2.5±1.1, 28.8±21.7 Classifier: C. Agee, UNM Type spec mass (g): 20.9 Type spec location: UNM Main mass: Dustin Dickens Comments: Field name DD-53; submitted by C. Agee, UNM |
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