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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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Mocs L6 (Romania,
fall, 1882). In the closeup on the right, saw marks are visible in the
metal grains.
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Two views
of a sawn slice of Independence L6
(Missouri, fall, 1917), with electronic flash lighting (LEFT, with
millimeter ticks on scale) and natural sunlight (RIGHT). Click
on image for enlargement. Thanks to Karl Aston for the sample.
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Two views
of a sawn slice of Cape
Girardeau H6 (Missouri, fall, 1846), with electronic flash lighting
from two dufferent angles. Click on image for enlargement. Thanks
to Karl Aston for the sample.
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Unnamed Northwest
Africa (NWA) H5 chondrite
A large slice of L4 chondrite Seminole. There are thousands of sub-millimeter
metal grains in this slice.
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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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Three views of the same stone, another
unnamed ordinary chondrite (probably H chondrite) from northwest Africa.
Above left: The unspectacular weathered exterior in direct sunlight.
Above right: A polished, sawn face in direct sunlight. All the
dark areas are alteration (rust) around the metal grains.
Right: The same face illuminated by a north-facing window. The
metal grains are more obvious in this view. The rock looks grayer
than it actually is in this view because of the polish and blue lighting.
It is likely that this meteorite fell thousands of years ago. |
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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.
On the right is one of many fragments
of an L5 ordinary chondrite from Algeria known as Northwest Africa
869. On the top, the fusion crust is still intact. Notice that it
is smooth with no holes. The rougher portion on the bottom of the
photo is where the fusion crust as broken off after it fell. This
meteorite probably also fell thousands of years ago and has been exposed
to harsh conditions in the desert.
Note that there is no obvious metal. L chondrites don't contain as
much metal as H chondrites. The rock is moderaly magnetic, however.
Click on image for enlargement (big). |
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Above left and right:
Two views (direct sunlight) of an unclassified ordinary chondrite
fragment from the Sahara desert. The fusion crust is dark and smooth.
If this were a fresh fall, it would be shinier. In most meteorites
the fusion crust is darker than the interior.
On the right is the weathered, broken face of the meteorite (electronic
flash lighting). Rusting of the metal grains has led to reddish staining.
Up close, shiny, unrusted metal grains stick out. Click on image for
enlargement (big). |
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carbonaceous chondrites
Only 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. |
