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2.9g HED Achondrite Meteorite amazing Howardite slice I NWA 15795
Top Meteorite
- $150.00
On Offer: 2.9 gram slice of the amazing HED achondrite howardite meteorite.
Type: HED Howardite
Description: 2.9 gram slice of HED howardite with a mix of approximately 65% eucritic material and 35% diogenitic material. Fusion crust can be seen on the outer part of the slice in two of the three sides of the slice.
Description: 23.80 gram end piece of an amazing orthopyroxenite diogenite. This diogenite has a coarse grained texture of mostly low-Ca pyroxene with several large black chromite crystals visible throughout the cut surfaces. Only a single small 86 gram gray-green stone was found with a small amount of remnant glassy black fusion crust on one side. This specimen represents the remaining main mass of this classification after analysis with only one smaller end piece available.
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.
What you get: 2.9g Howardite meteorite specimen as shown, shipping/storage membrane box & signed Certificate of Authenticity.
We offer a 100% no questions asked 30 day return policy.
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| Northwest Africa 15795 | |||||||||||||||||||||||||||||
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| Basic information |
Name: Northwest Africa 15795 This is an OFFICIAL meteorite name. Abbreviation: NWA 15795 Observed fall: No Year found: 2021 Country: (Northwest Africa) Mass: 343 g |
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| Classification history: |
This is 1 of 462 approved meteorites classified as Howardite. Search for other: Achondrites, , and |
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| Comments: | Approved 29 May 2023 | ||||||||||||||||||||||||||||
| Writeup |
Writeup from MB 112:
Northwest Africa 15795 (NWA 15795) (Northwest Africa) Purchased: 2021 Apr Classification: HED achondrite (Howardite) History: The meteorite was purchased in Mali by Mr. A. Selek in April of 2021 and sent to Mr. D. Dickens via post soon after. A piece of the stone was subsequently cut and sold by Mr. Dickens to Mr. D. Lorenzen along with a repository donation mass for classification. Physical characteristics: One rock completely covered in black fusion crust. Petrography: The meteorite is a complex polymict breccia composed of lithic and mineral clasts set into a fine-grained clastic matrix of related material. Lithic clasts are up to 2 cm sized diogenitic, up to 1.5 cm sized basaltic, and up to 6 mm sized dark impact melt clast. Predominant minerals are up to 1 mm sized diogenetic orthopyroxene (about 30%), ferroan low-Ca pyroxene, compositionally zoned low-Ca pyroxene, exsolved pyroxene and calcic plagioclase. Minor phases include silica, chromite, ilmenite, FeS, and metallic iron. Geochemistry: diogenetic pyroxene: Fs25.5±0.2Wo3.0±0.7 (Fs25.2-25.8Wo1.7-3.7, FeO/MnO=23-28, n=10); ferroan low Ca-pyroxene: Fs43.9±0.7Wo1.9±0.9 (Fs42.7-44.8Wo1.0-3.6, FeO/MnO=27-31, n=10); zoned low-Ca pyroxene: Fs43.4±10.0Wo3.5±2.0 (Fs27.4-52.9Wo1.3-8.0, FeO/MnO=28-34, n=10); low-Ca pyroxene host to augite exsolution lamellae: Fs52.0±0.3Wo1.5±0.1 (Fs51.7-52.2Wo1.4-1.5, FeO/MnO=27-29, n=10); augite exsolution lamellae: Fs19.6±0.6Wo44.7±0.7 (Fs18.6-20.8Wo43.7-45.7, FeO/MnO=23-28, n=10); calcic plagioclase: An84.5±3.3 (An79.8-90.4, n=12) |
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| Data from: MB112 Table 0 Line 0: |
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