[meteorite-list] getting oriented on orientation

[MeteorHntr 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
 



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