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Checklist
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Examples
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Caveats & Comments
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| The chance of finding a meteorite is exceedingly
small. |
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Most rocks aren't meteorites. |
| The chance of finding a meteorite that has
just fallen is even smaller. |
|
Since 1900, the numbers of recognized meteorite "falls" is
about 670 for the whole Earth. That's about 6 per year. Only
94 of those occurred in the US. That's less than 1 per year. |
| Not everything that falls from the sky is a
meteorite. |
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Read some stories. |
| Not every rock that looks like a meteorite is a meteorite. |
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It is not possible to determine whether a rock is a meteorite just
from appearance. |
| If it does not have a fusion
crust, then it's probably not a meteorite. |
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Some meteorites do not have obvious fusion
crusts, but that's rare. Usually there's fusion crust on at least
one face. |
| If it does have some kind of rind
or coating, the rind or coating is probably not a fusion crust
and the rock isn't a meteorite. |
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There are various processes on Earth that cause
rocks to have coatings. Some of these, particularly desert
varnish, can look remarkably like a meteorite fusion crust. |
| If it's got a thick rind or coating,
then
it's not a meteorite. |
|
Fusion crust are thin because as soon as the
exterior of the meteoroid melts, the liquid is sloughed off because
of the high velocity of the meteoroid. When the meteoroid slows
down, there's not enough heat to cause melting. |
| If it's big and it does not have
regmaglypts, then
it's probably not a meteorite. |
|
Not all meteorites have regmaglypts, however. |
| If it's angular, with sharp edges or points
and no smooth sides, then
it's probably not a meteorite. |
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For small meteoroids, 90% of the
mass is lost to ablation as it come through the atmosphere. Edges
and "corners" are the first parts to ablate away. Put
and ice cube in water an wait for 90% to melt. The "cube" that's
left will have no edges or points. It's like that with meteorites. |
| If it's stony (not an iron) and has a rough
exterior, then
it's probably not a meteorite. |
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| If it's stony (not iron) and has sharp protuberances,
then
it's probably not a meteorite. |
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| If it has veins, swirls, foliation, radiating
features, or tubes, then
it's not a meteorite. |
|
Rarely, there might be veins of impact melt
(see NWA 482). Some meteorites
have veins of metal. |
| If it's got layers, lamination, or any kind
of linear or planar features, then
it's definitely not a meteorite. |
|
Layered rocks occur on Earth because the Earth
has gravity. Most meteorites come from objects (asteroids) too
small
to have
any
appreciable gravity. If there is no gravity, then there is no
way to form layers.
Here is the only
exception I know about, and it's a terrestrial weathering effect.
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| If it contains elongated minerals or clasts,
then
it's probably not a meteorite. |
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Among meteorites of which I'm aware, MIL 05035
(an unbrecciated basalt) has the most elongated minerals; see photomicrograph.
It is exceedingly rare for the aspect ratio of a clast in a brecciated
meteorite to exceed 3-to-1. |
| If it's spherical, then
it's probably not a meteorite. |
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There are processes on Earth that lead to spheroidal
rocks (spheroidal weathering, tumbling and abrasion in water).
These processes don't occur where most meteorites come from. |
| If it contains round things, they're not necessarily chondrules. |
|
Lots of earth rocks contain round things. |
| If it's square, rectangular, or has flat sides,
then
it's probably not a meteorite. |
|
When meteoroids pass through the atmosphere, they tend
to get rouned, like ice cubes in water. |
| If it's got lots of holes in it, then
it's not a
meteorite. |
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Very few stony meteorites have vesicles or
holes. In those that do, the holes are sparse and small (Do a
Google search for photos of Ibitira and Dhofar
081.) Vesicles require gas. There's not much gas where most
meteorites come from. Iron meteorites often have holes, however. |
| If it contains amygdules or rounded clasts,
then
it's probably not a meteorite. |
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| If rock or mineral grains stand out from the
matrix or have been plucked out leaving a cavity, then
it's probably
not a meteorite. |
|
In many terrestrial sedimentary rocks, the
clasts are harder than the matrix. Sometimes they pop out of
the rock. That doesn't happen in meteorites. |
| If you found it on the beach, then
it's probably
not a meteorite. |
|
I am unaware of any meteorite that's been found
on a beach. |
| If you found it in a stream bed, along a river,
or any other place where there are lots of rocks, then
it's probably
not a meteorite. |
|
Successful meteorite hunters search for meteorites
in places where there ARE NOT a lot of rocks. If you want to find
your car easily, park it in an empty parking lot. |
| If you found it near a road or railroad track,
then
it's probably not a meteorite. |
|
It may have fallen off
a train or truck. |
| If it contains quartz, then
it's not a meteorite. |
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Quartz is the only common mineral that will
scratch glass. Try to scratch glass with a sharp edge of the rock.
If it scratches glass, its not a meteorite. |
| If the rock is "really hard," then it's probably
not a meteorite. |
|
Because meteorites don't contain quartz (the hardest common
terrestrial mineral), they're not all that hard. |
| If it consists of hematite or magnetite, then
it's not a meteorite. |
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Some highly weathered meteorites may contain
hematite. |
| If it's made of metal or looks metallic, then
it
might be a meteorite, but it's probably not. |
|
Human-made stuff like slags are often mistaken
for meteorites. |
| If the rock contains shiny things that look
like metal, but the rock is not magnetic, then the shiny things
probably aren't metal and the rocks isn't a meteorite. |
Some sulfide and oxide minerals look like metal. |
| If it attracts a magnet but does not contain
obvious metal, then it's not a meteorite. |
|
Meteorites are magnetic because they contain
iron metal. Earth
rocks don't contain iron metal. Many
Earth rocks are magnetic because they contain magnetite, however. |
| If it does not attract a magnet, then
it could still be a meteorite, but it is probably not. |
Many of the rarest types of meteorites are
not magnetic, but then neither are most Earth rocks. |
| If it's "heavy for it's size,"
then it
might be a meteorite, but it's probably not. |
|
The commonest
kind of meteorites, the ordinary
chondrites, is denser than
most Earth rocks because they contain iron metal. However, some
Earth
rocks
are
dense like
meteorites. To confuse the issue, some rare meteorites have low
densities like common Earth rocks. |
| If it's not heavy for
it's size, then
it might be meteorite, but it's probably not. |
| If it's reddish, particularly on the inside,
then it's probably not a meteorite. |
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Most meteorites are shades of grays
and browns. |
| If it's whitish, it's probably not a meteorite. |
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| If it's got polygonal or columnar jointing,
then
it's not a meteorite. |
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| If it's stony (not iron) and has a really goofy
shape, then
it's probably not a meteorite. |
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| If it's hollow, then
it's not a meteorite. |
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| If it does not look like other rocks in the
vicinity, then
it might be a meteorite, but it's probably not. |
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| If there's writing or a picture on it, then
it's
not a meteorite. |
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| If it's in a conspicuous place, then
it's probably
not a meteorite |
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| If it's radioactive, then
it's not a meteorite. |
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Meteorites are less radioactive than most Earth
rocks. |
| Many-to-most rocks sold over the Internet as
meteorites really are meteorites; some are not. |
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| If you find a real meteorite, it probably isn't
worth as much ($) as you think or wish. |
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| Meteorological is not the same as meteoritical. |
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