METEORITE OR METEORWRONG?ordinary chondritesAbout 63%* of all known meteorites are ordinary chondrites. Below are some photos of sawn faces of some ordinary chondrites in the Washington University collection. Click on the left-hand image for enlargement. The brightest materials in each photo are metal grains (veins in Richarton). Most ordinary chondrites contain metal and are consequently magnetic. |
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Identified
as "Richarton, ILL." possibly Richardton H5 (North Dakota, fall,
1918). In the closeup on the right, saw marks are visible in the metal vein. Notice that the metal grains are typically less than 1 millimeter in size. |
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Allegan H5
(Michigan, fall, 1899) |
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Mocs L6 (Romania,
fall, 1882). In the closeup on the right, saw marks are visible in the
metal grains. |
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Bjurböle
L/LL4 (Finland, fall, 1899) |
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Unnamed Northwest
Africa (NWA) H5 chondrite |
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Ordinary
chondrite pebbles found in the Sahara desert. Most are broken, but
a partial fusion
crust is intact on many of them. Notice that despite that all of them
contain metal, they are not rusty colored. |
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This meteorite violates a
number of the recognition principles that I stress in "A
Photo Gallery of Meteorwrongs." There is no obvious fusion
crust. The surface is not glassy or shiny; there are no regmaglypts.
The exterior has some ridges and one point. It's clearly a broken fragment
of a larger meteorite. If you look closely at the image on the upper left
(click on image to enlarge), however, there are shiny metal grains along
all the protuberances (points, ridges) because these areas have been abraded
from handling. Also, the specific gravity is 3.42,
well within the range of ordinary chondrites.
carbonaceous chondritesOnly about 2.5%* of all meteorites are carbonaceous
chondrites. Allende (below) is one of the most famous of carbonaceous
chondrites because it was observed to fall (February 8, 1969) and it was
large (more than 2 tons). Carbonaceous chondrites are only weakly magnetic. |
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Allende CV
(Mexico, fall, 1969), broken face (left) and sawn face (right). On the
left, some chondrules have been plucked out, but in the lower right corner
one is seen in positive relief. Click on images for enlargement. |
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