What are eucrites?

What are they important for?

View a list of fine Eucrites

A few asteroids have molten not too long after there formation.

Eucrites are a very interesting class of achondrites; many finds of them are thought to have originated from Vesta.

To understand how magmas migrated, erupted, and fractionated on these mostly smaller bodies helps us to understand what causes magma composition to change in general.

Asteroids with an appr. size of that of Vesta (appr. 500km diameter) could seriously be considered not to have completely evolved magmatic processes.  Although these rocks experienced significant (postcrystallization) impact shock these materials still  contain important information about the earlier stages of asteroidal and planetary

history and formation in our solar system as well as of thermal metamorphism (Metzler et al.; Yamaguchi). Several eucrites contain glass inclusions (tiny droplets of the molten rock, silica polymorphs,cristobalite and/or tridymite) trapped within mineral grains. These inclusions preserve information about magmatic processes and other thermal history data of the material.

updated: 11/25/2009

Please click below on any underlined meteorite title names to see more detailled descriptions

The original igneous pyroxene of cumulate eucrites was pigeonite, which has subsequently undergone subsolidus exsolution of augite and, in some cases, inversion to orthopyroxene, with additional augite exsolution. Hess and Henderson (1949) determined that original pigeonite in Moore County had only partially inverted to orthopyroxene: They described four pyroxenes in Moore County; low-Ca pigeonite developed from the original igneous pigeonite by exsolution of coarse lamellae of augite, and hypersthene developed from the low-Ca pigeonite through inversion and exsolution of fine lamellae of pyroxene phases. Harlow et al. (1979) found that the original igneous pigeonite in Serra de Mage had inverted to hypersthene, with development of four types of augite exsolution during the subsolidus cooling history. Similarly, in Moama the original igneous pigeonite has exsolved augite and inverted to hypersthene (Lovering 1975a Takeda et al. 1976). Binda is the most magnesian of the cumulate eucrites, and the only one classified by Delaney et al. (1984) as an orthopyroxene-cumulate eucrite. Takeda al. (1976) have shown that the original pyroxene in Binda was a low-Ca pigeonite that exsolved augite and inverted to hypersthene. Table 30 gives representative pyroxene analyses for selected cumulate eucrites, and estimated primary pigeonite compositions are plotted in Figure 42. As is the case for all HED meteorites, plagioclase in cumulate eucrites is calcic is on average more calcic than that in basaltic eucrites. Basaltic eucrite plagioclase has compositions in the range of bytownite to anorthite, while in cumulate eucrites the plagioclase is anorthite, An91-95;. A-881394 contains unusually calcic plagioclase, An,, {Takeda et al. 1997b). The K2O contents of cumulate eucrite plagioclases are very low typically <0.1 wt %.

The blue-metallic ilmenite occurs as small grains in most cumulate eucrites . Only in Moama ilmenite could not be found (Delaney et al. ,1984).

The composition of metal in the cumulate eucrites Binda, Moama, Moore County has received only cursory study (Duke 1965, Lovering 1964, 1975).

Based on modal abundances (Delaney et al 1984) cumulate eucrites can be divided into 2 subgroups:

a) feldspathic cumulate eucrites

b) orthopyroxene cumulate eucrites

There is a small but reasonable  possibility that  this meteorite might have originated Mercury

Anom. Eucrite with Mesosiderite tendency Dho 007

Black impact melt veins and pockets are abundant.

   Thermal history: Metal phases underwent a very slow cooling! (Yamaguchi et al)

This rare type is a cumulate eucrite, - a monomict breccia derived from a magmaticrock having a gabbroic texture consisting of subhedral grains of pyroxene

and plagioclase. Accessory minerals include metal, troilite, and chromite.

Dho 007 has a variety of glass inclusions (approximately up to 10 microns in diameter) contained in plagioclase  and pyroxene  grains as well as in the form a homogeneous melt. Gas bubbles formed from shrinkage during cooling can be found in the glass. The glass inclusions occur generally in round shape.

 Highly-silicic glass inclusions in Dho 007 and diogenites

orthopyroxenite. For Dhofar 007, formation of the inclusions in host plagioclase

from a late stage residual melt on the parent body. 

The occurrence of these secondary glass inclusions, outlining healed fractures in a single crystal, suggests migration of melts

Ref.:

Kouhei Kitazato+,,
and Masanori Kurosawa-

noncumulate eucrites

Most noncumulate eucrites have been considered as early crustal rocks of the HED parent body. Almost all noncumulate eucrites are metamorphic rocks.

Eucrites have been classified into 7 metamorphic types mainly based on the pyroxene mineralogy [1,2]. If eucrites were metamorphosed by burial of countless lavas during crust formation, the degree of metamorphism may be directly related to the timing of eruption [2]. Therefore, there might be a correlation between the degrees of metamorphism, bulk compositions, and radiometric ages [3,4]. For geochemical study, it is essential to examine unbrecciated eucrites or monomict eucrites since some “monomict eucrites” [5] (e.g., Pasamonte and Sioux County) have been reclassified into polymict eucrites [6,7]. A881747. The observation of the broken surface indicates that A881747 is mostly (~60-80%) composed of an angular subophitic lithology set in a gray matrix. The PTS displays a subophitic texture, consisting of coarse, lath-shaped plagioclase and anhedral, irregular pyroxene. The pyroxenes have a remnant Ca-zoning with closely spaced, thick (~10 µm) augite lamellae at the rim and sparsely sapaced (~50-100 µm in width) augite lamellae (~10 µm thick) in the core (i.e., type 4 [1]). Chemical compositions of pyroxenes vary from Wo4.8En35.5 to Wo41.6En30.3. Plagioclase in this rock is compositionally zoned from An89.0Or0.59 to An78.0Or1.7, similar to type 2 eucrites (e.g., Pasamonte clast) [6]. Analytical techniques: We obtained aliquots of powdered samples that were originally prepared from

et al. [2] suggested that types 5 and 6 eucrites may have been metamorphosed at ~1000 °C for a prolonged time to homogenize the Ca-Mg in the originally zoned pyroxenes, and those of types 4 and 7, which have remnant Ca-zoning in pyroxenes, could be less metamorphosed (peak metamorphic temperature <1000 °C). The strongly recrystallized texture of eucritic granulites [2] indicates that they may have been metamorphosed comparable to or more than types 5 and 6. Thus, we tentatively classified into the following groups: group A (types 1- 3), B (types 4 and 7), C (types 5 and 6), and D (eucritic granulites). Several eucrites (e.g., Ibitira and EET90020) experienced higher temperatures. However, since the heat source of metamorphism could have been shock-related, we excluded these eucrites from this classification.

Available are wonderful individuals @$14/g, and enpieces ($16/gr) from 15 - 35gr showing nice breccias: All legally exported.

Ask for best price and let us know your wishes of sizes; eric@mars.li

18°25′579′′N, 54°25′719′′E  Find: December 2005

Achondrite (eucrite, polymict)

History: Two pieces of meteorite weighing 898 g in total were found on a sandy surface in the desert of Oman. The distance between the fragments was about 30 m. Joined together, the fragments form an almost complete individual sample with ~10% missing.

Petrography: (Lorenz, Vernad and Brandstätter, NHMV) On the unbroken surfaces, black fusion crust is partly preserved. The meteorite is a polymict breccia consisting of fragments of medium- to coarse-grained metamorphosed gabbroic rocks and fine- to medium-grained subophitic basaltic rocks. Minor equigranular metamorphic pyroxene-feldspar rocks, melts, and melt matrix breccias are present. The rock fragments are situated in a fine-grained clastic matrix and comprise 60 vol% of the whole meteorite. Accessory minerals are troilite, chromite, ilmenite, silica, Ca phosphate, and metal Fe,Ni.

Geochemistry: Pyroxene (En35.1–62.8Wo1.8–5.7; Fe/Mn = 30) with exsolved augite (En21.1–54.2Wo21.1–38.9).

Specimens: A 20.6 g type specimen and one polished section are on deposit at Vernad. An anonymous finder holds the main mass.

Ask for best price for the slice above and let us know your wishes of sizes; eric@mars.li

0,2g sold; 1.2g slice sold; 1.231g slice 24x21mm $160; 3.67g endpiece with crust $430;

mostly with fresh sparling black crust

1 meteorite of 141g was found 10/2000 

S2 W1 61.1 2.5 Plag: An 89-91 20g Freiburg

ultrathin slices 1g 34x25mm $70; 1.8g $115

ask for fair price erich.haiderer@chello.at

no pairing - Available only through us!

Eucrite mon.- NWA 1895

3 fresh fragments with a tkW of 244g black fusion crust were found 2002 in Algeria TkW 244gr 21,2 Moderate Moderate 64,6 Mean An Mol % = 88.0, Range 85.1 - 92.2; O Oxygen isotopes: T13-14 d17O‰ = +1.873, d18O‰ = +3.890, D17O‰ = - 0.150;

A single stone of 18 g was found early 2002 in Western Sahara. Classification and mineralogy (A. Greshake and M. Kurz): a polymict breccia composed of large lithic and mineral clasts set into a fine-grained groundmass; lithic clasts are basaltic fragments and impact melt clasts; large mineral fragments are mostly plagioclase and exsolved Ca-pyroxene; plagioclase, An_83-91.5; pyroxene, Fs_29.7-58.5Wo_6.5-40.3; minor phases include orthopyroxene, silica, troilite, and ilmenite; low degree of shock; low degree of weathering. Main mass with anonymous finder; type specimen 3.7 g plus one polished thin section MNB.

ask for fair price erich.haiderer@chello.at

polymict eucrite (paired to Howardite) with a huge variety of distinct clasts;
Several eucrites of total 5009 g were found in the Western Sahara; Mineralogy: Pigeonite: Fs43.1-53.3Wo5.8-18.7; Plagioclas An87.5-92.3; Classification: Dr.A.Greshake, Humboldt University, Berlin, Germany; M.Kurz, Germany
part or complete slice, fragments or segment from $15/gr, slices 29/gr

NWA XXX - highly metamorphized eucrite

2,521g 25x24mm max. (is more a thin endpiece) no crust €70

2,422g 24x26mm max. crust €70

11,412g 59x45mm max. some crust €220

3,106g 40x31mm max. no crust €76

1.606g 25x14mm max. no crust €43

DaG 647 - unique eucrite with 2-stage thermal history, recrystallized, fresh like a Fall!! 

Ask for best price and let us know your wishes of sizes; eric@mars.li

PTS of DaG 647

$135/gr