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See contributor comments.   CV3

TKW 2 tons. Observed fall 8 February 1969, at the village of Pueblito de Allende, Chihuahua, Mexico.


 

Jürgen/jnmczurich writes:

The carbonaceous chondrite ALLENDE is a real "chunk of luck" for science.

Allende, fallen on February 8, 1969 in the province of Chihuahua in Mexico, contains numerous whitish and light color Ca/Al-rich inclusions, so-called CAI ^*. CAIs are early condensates from the solar nebula, which was very hot at least in certain areas (1500-1900K), but they are melted again several times and then built into the meteorite parent body.

In CAIs, the measurable isotopic compositions of many elements are anomalous, unlike what we know from previous measurements on meteorites and lunar material as well as on earthly rock samples. This indicates that part of this substance probably came from outside the solar system in an already condensed form, i.e. is older than our solar system. Therefore CAIs are the oldest imaginable substance.

The chemical composition of the Allende chondrite is primitive (in the sense of original, unchanged and undifferentiated), this can also be interpreted as if a piece of solar substance had been torn out of the sun, which then cooled and condensed...

When cutting Allende pieces, CAIs are always great surprises with regard to the distribution, size and shape of the different CAI types. The following few pictures show what kind of CAIs can be found on the outer surface of individuals and in slices.

^* The CAIs are enriched in highly refractory (heat-resistant) elements (Ca, Al, Ti, Zr, Ba, W, etc.) and have a mineralogical composition that is expected for the first high-temperature condensates from a gas with a solar composition. The minerals in these inclusions provide important information about the possible formation processes of solid matter in the formation phase of our solar system. The Allende meteorite is therefore of particular interest to science and is now one of the best-studied meteorites ever.

Minerals found in CAIs include Hibonite CaAl₁₂O₁₉, Perovskite CaTiO₃, and Melilite (Ca₂ (Al₂, Mg) SiO₇.

The above information is to the best of my knowledge.

The shown pictures were taken from my Allende collection samples. The slices were cut from my former 1.33 kg end section / half stone years ago in 2010 - special thanks for cutting support to my friend Marc Jost / Space Juwels Switzerland.

01 – Cutting Allende in 2010 with a wire saw
02 – Slices and one flat endsection. All gone today, sorry…
03 – Allende group of six pieces
04 – Allende group of six pieces – different view
05 – The large Allende individual hit the ground hard in 1969
06 – Angular CAI, 6 x 5 mm, on the outer surface of the large individual
07 – 16 x15 mm CAI on the surface of the large individual
08 – 16 x15 mm CAI on the surface of the large individual – side view
09 – Chondrule hole, diameter 5.5 mm, on the surface of the large individual
10 – Allende slice with dark inclusions and a chondrule-like CAI, diameter 6.5 mm
11 – Allende slice with different types of CAIs
12 – A rarly seen large 2mm bronce-colored Pendlandite inclusion (Fe,Ni)₉S₈. See also in pic 10