Identifying Meteorites: Differentiating Between Extraterrestrial and Earth Rocks

[256bits]

of course this chart doesn't include stony meteorites, which are very common

I interpret the flowchart as,
Stoney would be on the left hand side, and middle.

If the density is greater than other general rocks, it is probably contains iron, but not noticibly magnetic like an iron meterorite, so not a meterorite.
If a crust and lighter colour, it may be a stony or carbonaceous meteorite.

Top and to the right is iron meterite, which should surely be magnetic.

Of course, density, colour, etc is relative, as is the classification "stony".

 

[davenn]

If the density is greater than other general rocks, it is probably contains iron, but not noticibly magnetic like an iron meterorite, so not a meteorite.

don't forget the relatively common stony-irons

there's 3 main classes
stones, stony-irons and ironsalso just noticed a big mistake in there, see the circled part

DOH ... if some one saw it fall, then it has to be a meteorite !
D

 

[256bits]

don't forget the relatively common stony-irons

Which is somewhere in the middle section, in that mix of lefts, rights, and downs.
He is kinda loose with his boxes and yes's and no's.
There are two boxes asking if it is heavier than other rocks, and dark crust.
I suppose the chart is meant to eliminate rather than confirm identification.

DOH ... if some one saw it fall, then it has to be a meteorite !

I think he is trying to weed out someone 100% thinking a stone that hit the roof of the house has to be a meteorite. Could have been the neighborhood kids throwing rocks. I bet he gets people thinking it must be a meteorite if a rock rolls up to their feet while walking near a cliff face.

 

[davenn]

I suppose the chart is meant to eliminate rather than confirm identification.

almost seems that way huh

I think he is trying to weed out someone 100% thinking a stone that hit the roof of the house has to be a meteorite. Could have been the neighborhood kids throwing rocks. I bet he gets people thinking it must be a meteorite if a rock rolls up to their feet while walking near a cliff face.

hmmmmmmmmmmmmmmmmmm maybe ... but the normal definition of seeing it fall is seeing the flash in the sky

 

[256bits]

hmmmmmmmmmmmmmmmmmm maybe ... but the normal definition of seeing it fall is seeing the flash in the sky

Too far away to run to keep up with it to see it hit the ground. Superman maybe.

 

[davenn]

Too far away to run to keep up with it to see it hit the ground. Superman maybe.

many many meteorites are recovered after seeing the fall ( the flash across the sky)
I even have 2 friends here in Australia that make major efforts to get a bearing on the fall direction
etc so they can work out the approx. location of the fall then go and see if they can find anything

tis something guys do all over the world

 

[1oldman2]

many many meteorites are recovered after seeing the fall ( the flash across the sky)
I even have 2 friends here in Australia that make major efforts to get a bearing on the fall direction
etc so they can work out the approx. location of the fall then go and see if they can find anything

tis something guys do all over the world

Howdy, I read recently about some guys making a great find at Lake Eyre not long ago using that method, What luck!

 

[1oldman2]

From the site I got the flowchart from.

 

[davenn]

"True lies" ... wasn't that an Arnie movie ?? hahahaha

 

[256bits]

this is worth mentioning,

A statistical study of the rates of meteorite falls (5) suggests approximately 17 meteorites >0.1 kilograms (0.22 pounds) in size fall in Arizona, or an area of equal size, each year. Two to three of these samples weigh >1 kilograms (2.2 pounds) and are about the size of your fist. A meteorite weighing >10 kilograms (22 pounds) falls every 2 to 3 years. Thus, from the turn of the century, approximately 240 meteorites >1 kilograms in size are believed to have fallen in Arizona. Since Father Kino first arrived in the Tucson area (1687), approximately 790 meteorites >1 kilograms in size are believed to have fallen in Arizona. Of this large number of meteorites, only 32 have been recovered, and only 1 of these (the Holbrook http://www.lpi.usra.edu/science/kring/epo_web/meteorites/falls.htmlmeteorite ) was observed to fall (2).

which is the ,
http://www.lpi.usra.edu/
( Lunar and Planet Institute, Houston, Tx )

By Arizona, they mean any surface area the size of Arizona.
Going by that, generally, 1 out of every 32 meteorites collected have been falls.
And as mentioned, luck is part of being at the right place at the right time.

Tracking the meteor path( fireball ) across the sky can give an indication of where it originated in the solar system.

 

[256bits]

Oh, I wasn't aware that Old Man had gotten results back confirming it actually is a meteorite or iron nodule or that you have taken over his thread and reestablished the topic.

I made a decent attempt to fully answer his post to the best of my ability at the time (although I'm now on the fence). He made it clear that any opinions were welcome and so far hasn't discounted peoples efforts to answer the thread (like you just did to mine).

I can well imagine that people find a rock, note its odd shape, texture, look and feel, and conclude it has to have come from no where else than from space.

 

[davenn]

I can well imagine that people find a rock, note its odd shape, texture, look and feel, and conclude it has to have come from no where else than from space.

uh huh
I regularly get people coming to me with rocks and asking if they are a meteorites

 

[1oldman2]

I can well imagine that people find a rock, note its odd shape, texture, look and feel, and conclude it has to have come from no where else than from space.

Hi, Odds are extremely good (Astronomically actually) that the rock I opened the thread with will check out to be an iron nodule, I look at it as lottery winning odds, however as they say "someones got to win" so its worth checking out. I guess in the long run (very long run) its true all rocks as well as the rest of Earths elements do actually come from space, all I'm sure of at the moment is its definitely not a piece of bitumen.
An interesting look at reported meteorite finds in the US http://meteorites.wustl.edu/numbers_by_state.htm
Cheers all.

 

[1oldman2]

uh huh
I regularly get people coming to me with rocks and asking if they are a meteorites

Just curious, have any of the rocks people have brought you turned out to be meteorites?

 

[davenn]

Just curious, have any of the rocks people have brought you turned out to be meteorites?

no from memory, there was only one that looked remotely like a meteorite once I finally saw it "in the flesh" but wasnt
the others were easily dismissedDave

 

[Idaho Astro]

If it is, indeed, iron, then the streak test (rubbing it on unglazed porcelain, like the underside of a toilet lid or the back of a porcelain tile) is a pretty strong indicator. If it's terrestrial iron, it will either leave a dark gray streak (magnetite) or a blood red streak (hematite). A meteorite should leave no streak at all (as long as you are rubbing a clean part of it, not any rust that may have formed on the surface after it sat on the ground for years/centuries). So, file a clean spot first, then do your streak.

 

[JoeBrown]

I found something very similar softball sized parts were magnetic and weighed over 3700 grams and took it to the local college geology department and was told by the professor hey wasn't sure but thought it was banded iron. I still think I'll get a second opinion but your pic looks very much like what I found.