DiogeniteDiogenites belong to the evolved achondrite HED group that also includes howardites and eucrites. They are named after the Greek philosopher Diogenes of Apollonia, of the 5th century BCE, who was the first to suggest that meteorites come from outer space (a realization forgotten for over 2,000 years). They are Click on Term to Read More
OrthopyroxeniteA rock composed primarily of orthopyroxene. Non-terrestrial orthopyoxenites include diogenites and a single martian meteorite, ALH 84001, that was found in the Allan Hills region of Antarctica in 1984. ALH 84001 is a cumulate rock consisting of 97% coarse-grained, Mg-rich orthopyroxene, with small amounts of plagioclase, chromite, and carbonate. It Click on Term to Read More
(≥90 vol% orthopyroxeneOrthorhombic, low-Ca pyroxene common in chondrites. Its compositional range runs from all Mg-rich enstatite, MgSiO3 to Fe-rich ferrosilite, FeSiO3. These end-members form an almost complete solid solution where Mg2+ substitutes for Fe2+ up to about 90 mol. % and Ca substitutes no more than ~5 mol. % (higher Ca2+ contents occur Click on Term to Read More)
Purchased January 2003
no coordinates recorded A single, fusion-crusted stone weighing 40.1 g was found in the Sahara Desert and later acquired by a meteoriteWork in progress. A solid natural object reaching a planet’s surface from interplanetary space. Solid portion of a meteoroid that survives its fall to Earth, or some other body. Meteorites are classified as stony meteorites, iron meteorites, and stony-iron meteorites. These groups are further divided according to their mineralogy and Click on Term to Read More dealer in Rissani, Morocco. The meteorite, designated NWA 1821, was subsequently purchased by American collector N. Oakes and submitted for classification to the University of Washington in Seattle (A. Irving and S. Kuehner). A very large stone that is possibly paired with this one is in the collection of a Morrocan dealer, while the 7 gram NWA 1880, classified by A. Greshake and M. Kurz, is most likely paired as well.
This diogeniteDiogenites belong to the evolved achondrite HED group that also includes howardites and eucrites. They are named after the Greek philosopher Diogenes of Apollonia, of the 5th century BCE, who was the first to suggest that meteorites come from outer space (a realization forgotten for over 2,000 years). They are Click on Term to Read More
is an unbrecciated aggregate of coarse, yellow-green, translucent to opaque, orthopyroxene crystals, somewhat similar to the Tatahouine diogenite, but having smaller crystals. In contrast to most fragments of Tatahouine, patches of black fusion crustMelted exterior of a meteorite that forms when it passes through Earth’s atmosphere. Friction with the air will raise a meteorite’s surface temperature upwards of 4800 K (8180 °F) and will melt (ablate) the surface minerals and flow backwards over the surface as shown in the Lafayette meteorite photograph below. Click on Term to Read More
are distributed over the surface of NWA 1821. In further contrast, this diogenite exhibits a protogranular, crystalline mineralogy, and lacks the ubiquitous black shock veins present throughout Tatahouine. Other constituents present in NWA 1821 include troiliteBrass colored non-magnetic Fe sulfide, FeS, found in a variety of meteorites.
, magnetiteFe oxide, Fe2+Fe3+2O4, containing oxidized iron (Fe3+) found in the matrix of carbonaceous chondrites and as diagnostic component in CK chondrites. In CK chondrites, magnetite is typically chromian, containing several wt. % Cr2O3. Click on Term to Read More
, and aluminous ilmeniteTi-Fe oxide, TiFeO3, found in achondrites, lunar mare basalts, and shergottites. Ilmenite forms as a primary mineral in mafic igneous rocks. It crystallizes relatively early out of a magma before most of the other minerals, and as a result, the heavier crystals of ilmenite precipitate to the bottom of the magma Click on Term to Read More
, along with minor olivineGroup of silicate minerals, (Mg,Fe)2SiO4, with the compositional endpoints of forsterite (Mg2SiO4) and fayalite (Fe2SiO4). Olivine is commonly found in all chondrites within both the matrix and chondrules, achondrites including most primitive achondrites and some evolved achondrites, in pallasites as large yellow-green crystals (brown when terrestrialized), in the silicate portion Click on Term to Read More
and chromiteBrownish-black oxide of chromium and iron (Cr-Fe oxide), Cr2FeO4, found in many meteorite groups. Click on Term to Read More
An O-isotopic analysis conducted at the Geophysical Laboratory, Washington, DC (D. Rumble III, 2007) gave a value for Δ17
O of –0.269 ‰, within the range of diogenitesDiogenites belong to the evolved achondrite HED group that also includes howardites and eucrites. They are named after the Greek philosopher Diogenes of Apollonia, of the 5th century BCE, who was the first to suggest that meteorites come from outer space (a realization forgotten for over 2,000 years). They are Click on Term to Read More
. To see an alternative classification systemDefinable part of the universe that can be open, closed, or isolated. An open system exchanges both matter and energy with its surroundings. A closed system can only exchange energy with its surroundings; it has walls through which heat can pass. An isolated system cannot exchange energy or matter with
for the diogenites based on mineralogical and petrographical features, proposed by Beck and McSween (2010) and modified by Wittke et al.
(2011), click here
. The specimen of NWA 1821 shown above is a 0.069 g micromount. A close-up view of a 0.49 g partially cut fragment can be seen here
. The photos below show some views of the main massLargest fragment of a meteorite, typically at the time of recovery. Meteorites are commonly cut, sliced or sometimes broken thus reducing the size of the main mass and the resulting largest specimen is called the "largest known mass". Click on Term to Read More
Photos courtesy of N. Oakes