11.24g Eucrite Slice Monomict Basaltic Breccia
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- $ 225.00
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 of the diogenitic and eucritic material both in situ and during ejection events.
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.
| Northwest Africa 12929 | |||||||||||||||||||||||||||||
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| Basic information |
Name: Northwest Africa 12929 This is an OFFICIAL meteorite name. Abbreviation: NWA 12929 Observed fall: No Year found: 2016 Country: (Northwest Africa) Mass: 23.7 kg |
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| Classification history: |
This is 1 of 272 approved meteorites classified as Eucrite-mmict. [show all] Search for other: Achondrites, Eucrites, and HED achondrites |
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| Comments: | Approved 21 Nov 2019 | ||||||||||||||||||||||||||||
| Writeup |
Writeup from MB 108:
Northwest Africa 12929 (NWA 12929) (Northwest Africa) Purchased: 2016 Classification: HED achondrite (Eucrite, monomict) History: Purchased Dec. 2018 by Dustin Dickens in Morocco from anonymous dealer. Physical characteristics: Many identically appearing pieces, desert weathered exterior, broken surface reveals a dark, fine grained interior. Petrography: (C. Agee, UNM) Microprobe examination of a polished mount shows mild brecciation with approximately 60% pyroxene and 35% plagioclase. Many pyroxenes have exsolution lamellae. Minor silica and troilite observed. Shock melt veins are present. Geochemistry: (C. Agee, UNM) Low-Ca pyroxene Fs61.6±1.8Wo3.3±2.4, Fe/Mn=32±0, n=9; high-Ca pyroxene Fs36.7±9.5Wo33.4±10.9, Fe/Mn=31±0, n=4; plagioclase An89.4±3.1, n=7. Classification: Monomict basaltic eucrite, equilibrated. |
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| Data from: MB108 Table 0 Line 0: |
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| Institutions and collections |
UNM: Institute of Meteoritics MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 USA, United States; Website (institutional address; updated 12 Feb 2015) | ||||||||||||||||||||||||||||
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