[meteorite-list] getting oriented on orientation

From: MeteorHntr at aol.com <MeteorHntr_at_meteoritecentral.com>
Date: Wed, 5 Mar 2008 15:17:06 EST
Message-ID: <c5e.2d786869.350059c2_at_aol.com>

Hello Mike and all,

Mike, I like your suggestion.

Obviously, a large contributing factor in a the final shape of a meteorite,
has to do with it's original shape of the rock before the fireball (or as it
broke apart in flight). Some rocks are just destined to look better (more
nosecone or shielded in shape) than others. But that gets more into subjective
interpretation.

One challenge is that composition and weathering can play a part in the
appearance of a meteorite.

The Brenham Main Mass, while few would argue is not oriented, does not have
flow lines, or a roll over lip. The trailing side is noticeably more rough
than the nosecone, as it was not melted, but there is not "frothy" evidence of
bubbling on in the low pressure zones on the back side.

So, while it would not have ALL 5 or 6 or 7 or 8 potential characteristics
of being oriented, the evidence points that it indeed was 100% oriented in
it's flight, thus producing the shape it is in now, less a bit of wathering.
Also, I am not sure that a large pallasite would have the same ability as a
Eucrite would have in displaying the different potential characteristics?

So would the Big Brenham get a "lower grade" than a strange shaped
Millbillillie that might have more characteristics, yet not look even close to what
one thinks an oriented meteorite should be?

I think there are some characteristics that lead to a definite conclusion
that the rock did not tumble in flight.

I think if a dealer, or collector wants to represent their meteorite
specimen as oriented, they need to justify why they think it is, base on the
accepted criteria. Then it is up to the observer/buyer to evaluate the quality of
those characteristics.

Not all flowlines are the same. Not all roll over lips are the same. Not
all frothy crust on the trailing side is the same. Not all curvature of
leading edge is the same.

Are we going to then grade each charateristic on a scale of 1 to 5?

A description might then look like this.

"Based on the "IMCA 4-Point Scale of Orientation' this rock grades at a 2.25
out of 5 as follows:
Characteristic A: Flowlines Scale 1-5 = 4 note: flowlines over 60% of the
rock All from a radiant point
Characteristic B: Roll Over Lip Scale 1-5 = 2 note: Mild roll over lip on
25% of the edge
Characteristic C: Parabolic Curve Scale 1-5 = 3 note: curvature is on a 280*
curve on X axis, 264* on Y axis
Characteristic D: Bubbling trailing side Scale 1-5 = 1 somewhat different
texture on the back side
Total 4+2+3+1 = 9 / 4 = 2.25"

Or, you do like Mike Farmer mentioned, you call it oriented, and you supply
16 photographs to back up your point.

Or, you say, like Mike suggested: O3, O2 or O1, Completely, Partially, or
Some, and justify why.

My two flowlines worth.

Maybe we should set up a Crater grading scale while we are at it?

Steve Arnold
Arkansas




.
In a message dated 3/5/2008 11:17:41 A.M. Central Standard Time,
fuzzfoot at comcast.net writes:
Great suggestions, Darryl. I would go even a little less complicated and
suggest a 3 number rating system. Here are some quick, nut-shell definitions:

O3 - Completely oriented: Obvious and conclusive evidence that the meteorite
stabilized during entire flight.

O2 - Partially Oriented: Evidence that the meteorite stabilized during most
of flight, but also tumbled of axis.

O1 - Some Orientation: Evidence that the meteorite stabilized briefly at one
or several different points during flight, but tumbled majority of flight.

No Orientation - If no orientation is present, then there is probably no
need to mention it in description.

Other considerations: Where does 'dual orientation' fit in? I have had
numerous Sikhotes that have had 'bullets' or 'buttons' on both ends - evidence
that the they flopped like a pancake and partially stabilized on both opposing
edges.

Keep the suggestions coming.

Best,

Mike Bandli
www.Astro-Artifacts.com
 



**************It's Tax Time! Get tips, forms, and advice on AOL Money &
Finance. (http://money.aol.com/tax?NCID=aolprf00030000000001)
Received on Wed 05 Mar 2008 03:17:06 PM PST