Howardites


Howardites are the H class in the HED achondrite clan (howard-eucrite-diogenite). Howardites are polymict breccias composed of angular clasts of eucrites and diogenites welded together by pulverized mineral dust. They do not have unique mineral characteristics like other meteorite classes.

Surface of the NWA 776 howardite. Consists of eucrite fragments or clasts (example of white plagioclase and dark pyroxene eucrite shown in upper left), diogenite pyroxene grains (green), and clasts (dark). Height is 2 cm. Image © 2005 T. E. Bunch.

Howardite ALH 76005. Image © 2005 T. E. Bunch

Although larger asteroids are accepted as the parents of meteorites, in all but one case, it is impossible to link a specific meteorite with a known asteroid. The exception is the HED suite of meteorites which most scientists believe originated from the asteroid Vesta. Spectral images from the Hubble Space Telescope show that Vesta (525 km in diameter, the third largest main-belt asteroid) has a surface composition identical to eucrite meteorites while some deeper areas exposed by impacts are very similar to diogenites. Thin ejecta blankets on the asteroid are mixtures of both and are equivalent to howardites. Deeper rocks exposed on crater floors of Vesta are olivine-rich, although asteroidal meteorites of this composition have not been found to date. In 1996, the Hubble Space Telescope detected a huge crater on Vesta, 430 kilometers across and perhaps a billion years old, that may be the source of the HED suite of meteorites. Recently scientists have discovered a series of 5-10 km size asteroids with the same spectral features as Vesta, which probably represent ejecta from Vesta.

Vesta. These two surface maps of the asteroid Vesta are derived from Hubble telescope images taken between November 28 and December 1, 1994 and show surface details as small as 35 miles across. The top panel indicates sharp contrasts in Vesta's surface color. The surface markings may represent ancient volcanic activity such as lava flows and, in addition, regions where major collisions have stripped away the surface. The bottom panel reveals that the Vestan surface is made up of igneous rock, indicating that either the entire surface was once melted or lava flowing from its interior once completely covered its surface. Source: http://hubblesite.org/newscenter/newsdesk/archive/releases/1995/40/.

Vesta is a mini-planet where in its early history partial melting gave rise to layered plutonic rocks like diogenites after which melting in the near surface produced basaltic flows or eucrites. Impact mixing of these rocks made surface breccias or howardites. The age of the lava flows from which eucrites derived is 4.5 billion years old and less than 125 million years after the formation of the solar system. So, in its early history, Vesta's geological activity was intense, but very quickly became geologically inactive except for the effects of impacts that still occur today. Because of their much larger size, the geological evolution of true planets (Earth, Mars, etc.) has continued to the present. Dozens of Vesta-like asteroids probably existed at one time, but since then have been broken apart into smaller asteroids.

Spectral reflectance data for Vesta (above) allow construction of a geological map of the surface. Compare the bottom part of the figure with the Hubble map of Vesta (above). The upper part of this image shows the interpreted cross section of the asteroid. Credit: Harry Y. McSween, Jr., Department of Earth and Planetary Sciences, University of Tennessee. Source: http://geoweb.gg.utk.edu/Geology2003/Faculty/mcsween/displayimages/511.htm.

Summary of Howardite Characteristics

Howardites do not have unique mineral characteristics like other meteorite classes and are considered to be regolith breccias that consist essentially of >10 modal % of diogenites and <90 modal % of eucrites, some of which are very dark, shock-melted clasts. If a suspected howardite contains <10 modal % of diogenite and >90 % eucrite material the stone is classified as a eucrite. On the other hand, a stone that is <10 % eucrite and >90 % diogenite, it is a diogenite. Howardites may also contain minor components that include carbonaceous chondrites, in addition to minor exotic clasts.


Northwest Africa 776

Morocco
Purchased 2000
Achondrite (howardite)

A 49 g crusted stone was purchased in Morocco. Mineralogy and classification (T. Bunch and J. Wittke, NAU): a polymict breccia; contains large orthopyroxene fragments (Fs29Wo2) and clasts of eucrites, diogenites, gabbroic and glassy fragments; matrix divided into gray and very dark flow segregations; plagioclase, An87; shock stage, S3; weathering grade, W1. Specimens, 10.1 g and a thin section, NAU; main mass with buyer.

NWA 776. Image © T. E. Bunch, 2004


Northwest Africa 1150

Morocco
Purchased 2000
Achondrite (howardite)

NWA 1150. Image © T. E. Bunch, 2004

A 67.1 g stone was purchased in Tagounite, Morocco, by a meteorite collector. Classification and mineralogy (T. Bunch and J. Wittke, NAU): modal analyses on 24 cm2 show that 93 vol% of the clasts are diogenites, 7 vol% are basaltic eucrites. Diogenitic pyroxenes range from Fs28.1Wo2.5 to Fs7.8Wo11.3; plagioclase, An85-95, with ilmenite, chromite and sulfides. Eucrite pyroxenes range from Fe38Wo6 to Fs47.4Wo16.7; plagioclase, An88-92, with chromite (TiO2 = 0.68-3.48 wt%), troilite, and silica. Low weathering grade, W1. Specimens: type specimen, 21.1 g and one thin section, NAU; main mass is with the purchaser.

NWA 1150. Image © T. E. Bunch, 2004


Northwest Africa 1182

Morocco
Found 1999
Achondrite (howardite)

NWA 1182. Source: http://www.michaelbloodmeteorites.com/2_08NWA1182.jpg

A 780 g, mostly crusted specimen, was purchased in Morocco in 2000. Classification and mineralogy (T. Bunch and J. Wittke, NAU): medium clast size (<1.5 cm); clast modal analyses of 22 cm2 yield: diogenites, 82 vol%, ophitic to subophitic basalts 12%; shock melt, 4%; others, 2%. Diogenite clasts, orthopyroxene (Fs24Wo1.5) predominate over pigeonite (Fs30Wo8), plagioclase, An96, ilmenite, chromite and pyrrhotite. Shock stage, S2; weathering grade, W1. Specimens: type specimen, 20.3 g and one thin section, NAU; main mass is with the purchaser.


Northwest Africa 1695

Morocco
Found 2001
Achondrite (howardite)

A 614 g, fully crusted stone, was purchased in Morocco in 2001. Classification and mineralogy (J. Wittke and T. Bunch, NAU): clast size, <0.5 cm; clast modal analyses on 14 cm2 yields: subophitic basalts with large areas of symplectite crystallization, 80 vol%; diogenites, 9 vol%; fine-grained (< 0.2 mm) subophitic basalts, 6 vol%; other, 5 vol%. Orthopyroxene, Fs17-26 with exsolved pigeonite, Fs28-32Wo7-10. Common, Fe-rich subophitic clasts of plagioclase, An78, and ferroaugite, Fs40Wo39En21, with symplectic mesostasis of fayalite, ferrohedenbergite, sulfides, and SiO2 glass. Shock stage, S1, weathering grade, W1. Specimens: main mass with buyer, type specimen, 21 g with one thin section, NAU.


Northwest Africa 1914

Morocco
Found 2002
Achondrite (howardite)

NWA 1914 © T. E. Bunch, 2004

A 628 g, mostly crusted stone was purchased in Safsaf, Morocco, in 2002. Classification and mineralogy (T. Bunch and J. Wittke, NAU): fine to medium size clasts (<0.5 cm) of diogenites, typical eucrites, and FeO-rich olivine and pyroxene gabbroic clasts (up to 1.2 cm diameter). Clast modal analyses of 32 cm2 yield: diogenites, 46 vol%; eucrites, 34 vol%; gabbroic clasts, 10 vol%; shocked clasts, 6 vol%.; shock melted pyroxene and anorthite clasts, 4 vol%. Diogenite pyroxene: Ca-poor, En61Wo5 with lamellae of En40Wo16. Gabbroic olivine clast, Fa81-88; pyroxene, En24Wo17 to En10Wo26, plagioclase An89. Very fresh interior. Specimens: type specimen, 20.8 g, NAU; main mass, Hupé.

NWA 1914 © T. E. Bunch, 2004

NWA 1914 © T. E. Bunch, 2004


Northwest Africa 1929

Morocco
May 2003
Achondrite (howardite)

NWA 1929. Image © T. E. Bunch, 2004

History: A 922.2 g, partially crusted, complete stone was purchased in Erfoud, Morocco, in May 2003.
Petrography: (T. Bunch and J. Wittke, NAU). A breccia of 72 vol% cumulate eucrite clasts, 8 % subophitic clasts, 14 % diogenites, and 6 % melt clasts. Pervasive solid-state recrystallization of plagioclase and pyroxenes with localized melt pockets and veins in clasts.
Geochemistry: Coarse-grained gabbroic eucrite: Pyroxene (Fs45-40Wo7-20); plagioclase (An91.2-95.3); metal (Ni = 0.97; Cr = 0.87 [both wt%]). Diogenite: Pyroxene (Fs43-54Wo2.5-3.6; Fe/Mn = 36, 37).
Classification: Achondrite (howardite); high shock.
Specimens: A 22.02 g type specimen is on deposit at NAU. Farmer holds the main mass.

NWA 1929. (left) Original coarse grains of pyroxene and plagioclase seen in plane light were converted into recrystallized, fine-grained mosaics by shock-induced high pressures and temperatures. This is a solid state transformation; shock level S5-6. (right) The mosaicness of the pyroxene and plagioclase is revealed in crossed polarized light. Base width = 3 mm. Image © T. E. Bunch, 2004.


Northwest Africa 1939

Morocco
Found 2002
Achondrite (howardite)

A 100.4 g incomplete stone was purchased in Rissani in 2003 June. Classification and mineralogy (J. Wittke and T. Bunch, NAU): medium-grained howardite composed of basaltic eucrites (72 vol%), diogenitic pyroxenes (17 vol%), granular eucrites (8 vol%) and shock clasts. Diogenitic pyroxenes are mostly pigeonite (mean, Fs39.3Wo7.3). Basaltic pyroxenes are Fs32.4-47.8Wo3-11.6, plagioclase, An89.8, with ilmenite, silica, and chromite (Cr/(Cr+Al) = 0.61). Shock level, S1; slightly weathered. Specimens: 19.5 g, NAU; main mass, Farmer.

NWA-1939. Image width = 13 mm. Image © T.E. Bunch, 2007.


Northwest Africa 1942

Morocco
Found 2001
Achondrite (howardite)

NWA 1942. Image © T. E. Bunch, 2004.

Two stones, total weight 476 g, were purchased in Zagora in 2002 April. Classification and mineralogy (J. Wittke and T. Bunch, NAU): coarse-grained (diogenite clasts up to 12 mm); clast modes: diogenites 83 vol%, granular eucrites, 8 vol%, basaltic eucrites, 2 vol%, and shocked clasts, 7 vol%. Diogenite pyroxenes, Fs16.8-41.3Wo1.2-9.8); plagioclase clasts, An92, metal, Ni = 5.9 wt%, Co = 1.75 wt%. Shock level, S2; slightly weathered. Specimens: 34.2 g, NAU; main mass, Farmer.

NWA 1942. Image © T. E. Bunch, 2004.


Northwest Africa 1943

Morocco
Found 2001
Achondrite (howardite)

NWA 1943. Image © T. E. Bunch, 2004.

A 1220 g complete stone was purchased in Erfoud in 2002 April. Classification and mineralogy (T. Bunch and J. Wittke, NAU): mostly fine-grained with rare, large clasts of fine-grained eucrite breccias. Clast modes: diogenites, 44 vol%; basaltic eucrites, 17 vol%; cumulate eucrites, 13 vol%; basaltic breccias, 6 vol%; and shocked clasts, 20 vol%. Diogenite pyroxenes, Fs22.5-57.3Wo3-13.5); chromite, Cr/(Cr+Al) = 0.63 and metal, Ni = 5.4 wt%. Remarkably fresh with shiny crust and no oxidation around metal grains. Specimens: 22.5 g, NAU; main mass, Farmer.


Northwest Africa 2060

Morocco
Found 2003
Achondrite (howardite)

NWA 2060. Image © T. E. Bunch, 2004.

A 985 g, very fresh stone with shiny fusion crust, was purchased in Rissani, July 2003. Classification and mineralogy (T. Bunch and J. Wittke, NAU): a howardite of unusual characteristics. Fine-grained and powdery, average clast/grain size is <2 mm with few clasts >3 mm. Clast modes: diogenites, 74 vol%; eucrites 20 vol% (12 % cumulate, 8 % basaltic); anorthositic-like clasts, 3 vol%, shock melt clasts, vol. 2 % and opaques, vol. 1 %. Diogenite orthopyroxene, Fs35.6-38.8Wo2.3-4.2; plagioclase, An87; chromite, Cr/(Cr+Al) = 0.81; metal, Ni = 0.67 wt%. Melt inclusions in orthopyroxene contain Ca-rich pyroxene, Fs33.3Wo37.5, phosphate, silica phase, and K-rich glass. Plagioclase-pyroxene cumulates, Fs38.2Wo21; plagioclase, An86. Other eucrite textures include recrystallized, granular, ophitic, subophitic, and variolitic (Fs31.6Wo7 and Fs61.8Wo33). Plagioclase-rich clasts have 95 vol.% plagioclase (An96.1). Shock level, S2; no apparent oxidation or Fe-staining. Specimens, NAU 26 g; main mass, Boswell.

NWA 2060. Image © T. E. Bunch, 2004.


Northwest Africa 2132

Northwest Africa
Purchased 2004
Achondrite (howardite)

NWA 2132. Image © T. E. Bunch, 2004.

A large, complete stone of 1006 g was purchased in Rissani, Morocco in January 2004. Description and classification (T. Bunch and J. Wittke, NAU): fine to medium sized (<1 mm to 5 mm) clasts of diogenite pyroxenes; felty, granular, subophitic and cumulate basalts. Large diogenite pyroxenes are strongly zoned from cores of Fs30.5Wo2.4 to rims of Fs46.8Wo6.7; cumulate orthopyroxene, Fs60.7Wo2.7 with exsolved augite, Fs31.2Wo37.7, FeO/MnO = 29.7; plagioclase, An88.1; chromite, Cr/(Cr+Al) = 84.8; subophitic orthopyroxenes cluster around Fs54.6Wo3.6, FeO/MnO = 28.3. Shock level, S3; slightly weathered. Specimens: 20.9 g, NAU; main mass, Boswell.

NWA 2132. Image © T. E. Bunch, 2004.

NWA 2132. Image © T. E. Bunch, 2004.


Northwest Africa 2379

Northwest Africa
Purchased 2004 August
Achondrite (howardite)

A 68 g stone with fusion crust was purchased in Erfoud, Morocco. Description and classification (T. Bunch and J. Wittke, NAU): an unusual howardite that contains an array of plastically deformed shocked eucrite and diogenite clasts. Shock characteristics range from crushed cataclastics (S2-4), maskelynite-bearing (S4), recrystallized pyroxenes and plagioclase (S5) to melt clasts (S6) that contain olivine as the quenched mafic phase in place of typical pyroxenes. Diogenites: orthopyroxene, Fs25.0Wo2.9 (FeO/MnO = 29.4); plagioclase, An88.8; chromite, Cr/(Cr+Al) = 76, Mg/(Mg+Fe) = 24. Eucrites: orthopyroxene, Fs47.8-61.4Wo1.4-2.3 (FeO/MnO = 31.2-36); pigeonite, Fs51.3-56.8Wo7.7-12.6; augite, Fs27Wo28.1; plagioclase, An86.4-91.1. Quench olivine (<0.05 mm in diameter): cores, Fa17.9; rims, Fa36.4 (FeO/MnO = 41-47); low weathering grade. Specimens: type specimen, 13 g, NAU; main mass, G. Hupé.


Northwest Africa 2641

Northwest Africa
Purchased 2004
Achondrite (howardite)

A complete and crusted 97 g stone was purchased in Erfoud, Morocco. Description and classification (T. Bunch and J. Wittke, NAU): fine to medium-grained (~1.5 mm) howardite with a modal content of (in vol%): diogenites, 65; cumulate basalts, 24, subophitic basalts, 6 other, 5. Diogenite orthopyroxenes, Fs12.7-24Wo0.6-2.7 (FeO/MnO = 27.1-30.3); cumulate basalts, Fs29-57.4Wo1.9-3.7; cumulate basalt chromite, Cr/(Cr+Al) = 0.82. Shock level, S2-3, low weathering grade. Specimens: type specimen, 18.8 g, NAU; main mass, Reed.

NWA 2641. Base width = 13 mm. Image © T. E. Bunch, 2010


Northwest Africa 2644

Northwest Africa
Purchased 2004
Achondrite (howardite)

A 216 g dark, crusted stone was purchased in Erfoud, Morocco in August 2004. Description and classification (T. Bunch and J. Wittke, NAU): composed of typical cumulate and basaltic eucrite clasts and large (up to 2.8 mm diameter), very dark shock-melt and breccia clasts of glass, quench crystals, and shocked diogenite and eucrite fragments, all set in a very light-colored and fine-grained matrix. In addition, irregular to sub-rounded metal grains up to 3 mm in diameter, are present within the shocked clasts and randomly distributed in the matrix. Diogenite orthopyroxene, Fs21.3-29Wo0.8-3.1 (FeO/MnO = 24.5-32.4); shocked clast pigeonite, Fs29.1-31.8Wo3.4-6.1 (FeO/MnO = 30.2=33.4); cumulate pyroxene, Fs51.4-56.4Wo2.9-3.8; large plagioclase fragments, An90-94.2; metal, Ni = 4.4-18.3 wt%. At least two regolithic lithologies are represented. Low-grade weathering and low level shock; shock-melt/breccia clasts experienced shock to S6. Specimens: 22.0 g type sample, NAU; main mass, Oakes.


Northwest Africa 2752

Algeria
Find: 2004
Achondrite (Howardite)

History and physical characteristics: A 28 g partially dark crusted stone was found in Algeria in 2004 and purchased in Rissani, Morocco in 2005.
Petrography: (J. Wittke and T. Bunch, NAU) Contains a variety of basaltic clasts that range from microbasalts, subophitic basalts, to cumulate varieties. Coarse-grained cumulate clasts show a shock level range from S1 to S5. Similarly, diogenite fragments show a wide shock level range and a few contain exsolution lamellae of subcalcic augite. Mineral compositions: Eucrite orthopyroxene is Fs46-62Wo2.4-3.3, FeO/MnO = 27-30; exsolved pigeonite, Fs40-51Wo5.6-11.5. Diogenite fragments, Fs25.4-28.5Wo2.0-3.7; FeO/MnO = 31-33. Also contains chromite, Cr/(Cr+Al) = 0.84-0.88, ilmenite, FeS, silica, and a trace of metal.
Classification: Achondrite (howardite).
Type specimen: A total of 5.9 g is on deposit at PSF. Mr. Matt Morgan is the holder of the main mass.

NWA 2752. Eucrite and diogenite brecciated debris. Image © T. E. Bunch, 2007.


Northwest Africa 2792

NWA 2792. Image width = 17 mm. Image © T. E. Bunch, 2007


Northwest Africa 2794

Northwest Africa
Purchased 2005
Achondrite (howardite)

History: A 145 g single stone with partial fusion crust was purchased in Erfoud, Morocco, in 2005.
Petrography: (J. Wittke and T. Bunch, NAU) Contains fine to medium cumulate basalt clast size (<3 mm diameter) and even finer-grained subophitic basalts (<1 mm) with diogenite fragments up to 8 mm.
Geochemistry: Cumulate basalt pyroxenes: Orthopyroxene (Fs49.4-64.7Wo2.1-2.5), exsolved pigeonite (Fs45.1-54.4Wo13.1-6.7), Ca pyroxene (Fs36.0-47.1Wo19.6-24.1). All pyroxene FeO/MnO = 29-34 (N=27). Diogenite: Orthopyroxene (Fs26.7-30Wo2.2-2.5; FeO/MnO = 24-30).
Classification: Achondrite (howardite); moderate weathering and low to moderate shock.
Specimens: A 21.4 g type specimen is on deposit at NAU. G. Hupé holds the main mass.

NWA 2794. Base width = 13 mm. Image © T. E. Bunch, 2010


Northwest Africa 2853

Northwest Africa
Found 2005
Achondrite (howardite)

History: A 1006 g fully crusted stone was purchased in Erfoud, Morocco, in 2005.
Petrography: (T. Bunch and J. Wittke, NAU) Contains heterogeneously distributed orthopyroxene fragments that tend to be large (2-9 mm in diameter). Diogenite modes for three thin sections give 0, 9, and 15 vol%. Eucrites have a fine- to coarsegrained size range and consist of subophitic and cumulate textured basalts. Most pyroxenes recrystallized into small, polygonal aggregates; plagioclase melted, although original grain boundaries are preserved and crystallized into fine-grained fibrous to radiating textures.
Geochemistry: Host: Pigeonite (Fs45.3-51.7Wo5.8-9.0; FeO/MnO = 29-33), exsolution lamellae (Fs33.6-39.4Wo19.0-25.4). Diogenite: Orthopyroxenes (Fs22.6-25.6Wo1.8-2.3; FeO/MnO = 24-27), plagioclase (An89-94.3).
Classification: Achondrite (howardite); high shock.
Specimens: A 22 g type specimen is on deposit at NAU. Regelman holds the main mass.

NWA-2853. Image width = 13 mm. Image © T.E. Bunch, 2007.


Northwest Africa 2912

Northwest Africa
Found 200?
Achondrite (howardite)

NWA-2912. Image width = 13 mm. Image © T.E. Bunch, 2007.


Northwest Africa 2913

Northwest Africa
Found 200?
Achondrite (howardite)

NWA-2913. Image width = 13 mm. Image © T.E. Bunch, 2007.


Northwest Africa 3117

Northwest Africa
Found 2003
Achondrite (howardite)

NWA 3117. Image © T. E. Bunch, 2004.

Three stones that weigh a total of 2.45 Kg were purchased in Erfoud, Morocco in December 2003. Description and classification (J. Wittke and T. Bunch, NAU): howardite breccia of fine-to medium clast size (<3.0 mm); very heterogeneous distribution of diogenite clasts; cumulate basalt clasts were probably derived from the same basaltic provenance. All clasts are highly shocked (shock level 3-6): pyroxenes and plagioclase were subjected to shock-induced, solid-state recrystallization; a few have completely melted. Eucrite pigeonite, Fs47.3-52Wo16.7-7.7; Ca-rich pyroxene, Fs40Wo25.2, Fe/Mn = 28.5; plagioclase, An90.7-92.0; chromite, Cr/(Cr+Al) = 0.80, Fe/(Fe+Mg) = 0.95; metal, Ni = 1.99 wt%; ilmenite and silica. Diogenite orthopyroxene, Fs48.4-54.9Wo1.1-2.7, Fe/Mn = 32.5. Possibly paired with NWA 1929. Low weathering grade. Specimens: 3.8 g, NAU; 21.4 g, UCLA; main mass, Hupé.


Northwest Africa 4289

Algeria
Find: 2005
Achondrite (howardite)

History: A 14.7 g stone was found in Algeria in 2005 and purchased in Erfoud, Morocco, in November 2005.
Physical characteristics: Relatively fresh fusion crust covers the entire 14.7 g stone with the exception of tiny impact spallation areas.
Physical characteristics: Fine-grained breccia, clast size <4 mm, composed of eucrite basalts, diogenite and impact melt clasts.
Geochemistry (J. Wittke and T. Bunch, NAU): Subophitic basalt host pigeonite is Fs57.6Wo7.1. FeO/MnO = 34, exsolved augite is Fs21.7Wo41, and plagioclase is An92. The diogenite pyroxenes compositional range is Fs21.7-26.8Wo1.6-4.1, FeO/MnO = 28-30.
Classification: Achondrite (howardite).
Type specimens: A total of 3.7 g and one thin section are on deposit at NAU. Thompson is the main mass holder.

NWA 4289. Image width = 23 mm. Image © T. E. Bunch, 2007


Northwest Africa 4826

Northwest Africa
Find: 2006
Achondrite (howardite)

History and physical characteristics: A 344 g fully crusted stone with fine-grained, light grey interior was purchased in Tucson at the Tucson Gem and Mineral Show in January 2007.
Petrography (T. Bunch and J. Wittke, NAU): Consists mostly of two major eucrite lithologies and diogenite fragments that display complicated sector and reverse zoning. The medium- grained cumulate eucrite (lithology A) is enriched in ilmenite and chromite and contains polygonized pyroxene, plagioclase is partially converted to maskelynite. Eucrite lithology (B) is less shocked and contains pigeonite with well-developed exsolution lamellae and is present as matrix fragments. Diogenite fragments consist of those that are unzoned, those that are sector zone, and several large fragments that show dramatic reverse zoning and patches of augite. The weathering grade is low and the shock is S2-S5.
Mineral compositions: Lithology (A) orthopyroxene host, Fs50.3Wo1.3 (FeO/MnO = 31), lamellae, Fs23.7Wo45.2; chromite Cr/(Cr+Al) = 0.63; and plagioclase is An93.8-97.8. Lithology (B) Ca-poor pyroxene is Fs40.2Wo4.6 (FeO/MnO = 29) and the lamellae are Fs28.3Wo30.1. Sector zoned orthopyroxene cores are Fs25.3Wo2.6 (FeO/MnO = 28) and rims are Fs36.9-44.6Wo2.3-3.2. Most pigeonite cores with reverse zoning are Fs45Wo14, rims are Fs32.5Wo19, and included augite is Fs29Wo35.7. One FeO-rich orthopyroxene grain has a core of Fa70.5Wo2.8 (FeO/MnO = 35) and a rim of Fs56.6Wo2.8.
Classification: Achondrite (howardite).
Type specimen: A 21.3 g specimen is on deposit at NAU. The main mass holder is anonymous.

NWA 4826. Image © T. E. Bunch, 2007


Northwest Africa 4869

Algeria
Find: 2006
Achondrite (howardite)

History and physical characteristics: A 191g dark brown stone with little fusion crust was purchased in Morocco in July 2007 by A. Aaronson.
Petrography (J. Wittke and T. Bunch, NAU): A complex breccia of coarse-grained SiO2-rich cumulate and basaltic eucrites, microbasalts, FeO-rich ferrosilite/hedenbergite/fayalite lithologies, shock melt clasts, and diogenitic pyroxene fragments that comprise 14 vol% of the stone. A silica polymorph is enriched in many of the eucrite lithologies and may account for up to 15 vol% of cumulate basalts and as much as 21 vol% of medium to fine-grained basalts. The shock level is high (S4-S5) with most plagioclase present as maskelynite. Weathering grade is moderate.
Mineral compositions: Subophitic orthopyroxene host, Fs53Wo4.5 (FeO/MnO = 26); exsolved augite, Fs26.3Wo44; plagioclase (maskelynite), An92. Cumulate unexsolved pigeonite, Fs45.5Wo12.6 and maskelynite, An84. Silica - rich basalt host pyroxene, Fs61.1Wo3.1; lamellae, Fs32.7Wo42; olivine, Fa60.6 (FeO/MnO= 44); maskelynite, An69. Diogenitic pyroxenes, Fs28-34.4Wo1.1-1.4 (FeO/MnO= 29). Minor minerals include chromite, Cr/(Cr+Al) = 0.78-0.88, merrillite, Ni-poor metal, ilmenite and FeS. All analyzed maskelynite has plagioclase stoichometry.
Classification: Achondrite (howardite).
Type specimen: A total of 20.1 g are on deposit at NAU. Mr. A Aaronson holds the main mass.


Northwest Africa 5199

Algeria
Find: 2007
Achondrite (howardite)

History and physical characteristics: A 298 g medium gray, fully crusted stone was purchased at the Tucson Gem & Mineral Show in January 2007.
Petrography (T. Bunch and J. Wittke, NAU): Breccia-within-breccia with light tan to light gray clasts. Matrix is composed of eucrite and diogenite debris (typically <1 mm) together with prominent larger clasts of shock-melted eucrites. Modal content of diogenite is 88 vol% and eucrites are 12 vol%. Low-grade weathering and the shock level is S3-S5.  Plagioclase is crystallized from glass and most pyroxenes show reduced birefringence, shock lamellae and decorated planar deformation features. Shock melted diogenite clasts contain orthopyroxene fragments set in a quench –melt matrix.
Mineral compositions: Unzoned diogenite orthopyroxene is Fs29.1Wo3.0, FeO/MnO = 32, zoned example is core = Fs32Wo1.8 with FeO/MnO = 40 to rim of Fs47.6Wo1.8 and FeO/MnO = 31. Eucrite cumulate basalt low-Ca pyroxene is Fs46.3Wo5.0; FeO/MnO = 29 with exsolved augite Fs18.7Wo47. Chromites cr# range from 61-68. Plagioclase is An86-90.
Classification: Achondrite (howardite).
Type specimen: A total of 21 g is on deposit at NAU. The holder of the main mass is anonymous.


Northwest Africa 5222

Algeria
Find: 2007
Achondrite (howardite)

History and physical characteristics: A small 60 g stone with little fusion crust and a heavily wind ablated surface was purchased in Erfoud, Morocco in October 2007.
Petrography (J. Wittke and T. Bunch, NAU): A howardite with many basaltic and at least two diogenitic lithologies together with many heavily shocked, dark clasts. One cumulate basalt contains maskelynite. One diogenite lithology contains 23 vol% plagioclase.
Mineral compositions: Subophitic basalt pigeonite is Fs55.9Wo7.8 (FeO/MnO = 30) and single grains of augite are Fs28.3Wo34.6. Low FeO cumulate basalt orthopyroxene is Fs34.6Wo3.8 (FeO/MnO = 26). Diogenite orthopyroxene is Fs22.6Wo2.0 (FeO/MnO = 33).
Classification: Achondrite (howardite).
Type specimen: A total of 12 g is on deposit at NAU. The main mass holder is Cimala.


IDLocationDateClass.Mass (g)StatePyroxenesComments
NWA 2654Erfoud, Morocco2004HOW17,000S3-6Fs44.3Wo6.0 & Fs48Wo2.3paired with NWA 1929
NWA 2696Erfoud, Morocco2004HOW6,572S36Euc: Fs41-46Wo8-20paired with NWA 1929
NWA 2698Erfoud, Morocco2004HOW134S3-5, W2Euc: Fs40-47.2Wo7-18paired with NWA 1929