The Allende CV3 meteorite contains many components. Here are some less common chondrules, a collection from three Allende thin sections. Except for the last two, the views are 3.1 mm wide. The others are 0.9 mm and 1.1 mm wide details. All are in cross-polarized light. The first chondrule is also shown in Richard Norton’s The Cambridge Encyclopedia of Meteorites,
Dar al Gani 978 resembles CR chondrites in that it has relatively large chondrules which contain blebs of metal. Certain elemental abundances resemble those of CM–CO chondrites and others are similar to the CV–CM–CO range. O-isotope data are similar to CO and CV chondrites. DaG 978 is a type-3 ungrouped carbonaceous chondrite.
CO3s, carbonaceous chondrites of the Ornans type, contain the smallest chondrules of any of the major chondrite types. Still, chondrule sizes vary among CO3s. And within this CO3 there is a variety of chondrule sizes and a great variety of chondrule types and other matter. It is good to be observant when scanning a thin section of this material at
Tissint is the fifth witnessed Martian meteorite fall. It is a Shergottite. Many pieces totaling over 7 kg fell east of Tata, Morocco about 2 AM, July 18, 2011. The stones have a shiny black fusion crust which is glossier over olivine macrocrysts. Olivine macrocrysts and microphenocrysts are held in a finer groundmass of pyroxene, plagioclase (shocked to maskelynite) and other minerals. Small melt
A 6.2 kg stone was found in 1943 by a man cultivating a cotton field three miles south of Axtell, Texas. The family kept it until 1993 when it was bought by Blaine Reed and distributed. Except for some coloration from terrestrial weathering, it appears very similar to Allende. Close study shows that they are not paired. Axtell belongs to
Dellen Crater is a roundish lake system in central Sweden near the east coast 180 miles north of Stockholm. It is about 11 miles across. The impact that formed it occurred 89.0 ± 2.7 million years ago. Some of the impact rock from the site is called tagamite. It is a term that was introduced in 1975 to describe impact
CK chondrites, Karoondites, contain objects that hint at the processes that produced the rocks we have in our collections. Here are a few.
NWA 5930 CV3 is interesting for the variety of chondrules, including non-textbook chondrules, it contains. Some are misshapen, several are rather large and relict grains are common. The textural contrasts are remarkable.
The namesake of the Coolidge grouplet of meteorites was found in 1937 and has been classified H4, CV4 and C3.8-ung. Studies distinguish Coolidge from CK chondrites (which contain type 4 examples) and from CV chondrites. Some chondrules are large and layered from repeated accretion and heating in the solar nebula.
Angrites are achondrites consisting largely of augite. Augite is a pyroxene containing calcium and, in this case, some titanium and aluminum. Olivine and plagioclase make up the remaining bulk. Angrites are among the oldest known igneous rocks and probably came from a large parent body. Here are four photos each of three different angrites D’Orbigny NWA 2999 and a
It seems understatement to say that Almahata Sitta is polymict given that it contains at least twelve lithologies. Since the lithologic types are dominated by ureilites, though, it is classified as a polymict ureilite. Much of the remainder is EL and EH chondrites of various petrographic grades, melts and breccias. Also found are H and L ordinary chondrites and a
NWA 6007 is terrestrially fresh but shocked. It has well defined chondrules as you would expect of an L3.5. Compression has caused an orientation of components within the stone. Dark inclusions are scattered throughout.
NWA 5958 C3.0-ung was 286 grams of fragments. We bought a fragment from Greg Hupé and had thin sections made from it. The Met Bull entry and two papers are here: http://www.lpi.usra.edu/meteor/metbull.php?code=50844 http://www.lpi.usra.edu/meetings/lpsc2011/pdf/2343.pdf http://www.lpi.usra.edu/meetings/lpsc2011/pdf/2325.pdf
Mesosiderite meteorites are stony irons with roughly 50-50 proportions of each. The iron is asteroidal core and the stone is the crust of a differentiated asteroid. Mantle material is rare. Several formation scenarios have been proposed and scientists continue to discuss the matter. Mesosiderites are classified by mineralogy and texture. Estherville is an A3/4. That is, plagioclase content of the
Sometimes melt rock in meteorites contains blebs of metal-troilite (FeS) intergrowths. Here are examples from two rocks. NWA 869 is the well known L3-6 regolith breccia. It took a pounding on the surface of its parent body and contains a variety of clasts including melt rock. All 95 grams of NWA 6579 is melt rock. The composition of its olivine
