[meteorite-list] Australites/Philippinites - grooving - any info?

From: Aubrey Whymark <tinbider_at_meteoritecentral.com>
Date: Mon, 5 Feb 2007 05:42:01 +0000 (GMT)
Message-ID: <67437.47916.qm_at_web26303.mail.ukl.yahoo.com>

Hi list
   
  I wondered if there is anyone on the list who has collected a lot of australites and knows about the grooving on these tektites. What does it look like? Is it generally on the anterior side? Is it associated with particular shapes and not others?
   
  I am really interested to understand how australite morphologies fit in with the classic lenticular and breadcrust philippinites, which have grooving on only one side. I was also fascinated by the recent emails on stretch tektites.
   
  The more I look at philippinites, the more I think the U grooves are an original feature as oppose to chemical weathering. The U grooves occur on only one side and, when better developed, have a polygonal structure. I know this is usually explained as being the anterior side with flakes coming off due to thermal expansion/contraction, but I still wonder if that is the case. I wonder if these cracks developed (?perhaps as the tektite cooled) but the interior remained plastic. When this interior became solid, the solid would take up less space than the liquid. So, when it cooled totally did it 'suck' in at the grooves. I saw a similar thing when playing with solid and liquid wax. Are the grooves on one side then lost due to ablation, thus making the smooth side the anterior? Are these grooves in anyway similar to the starburst ray skin-splits featured on 'The Tektite Source' webpage? I understand this idea creates more problems, such as why do tektites from Vietnam area not
 show polygonal cracks like philippinites. I'm sure there is still much to be learnt, but if anyone knows answers I'm keen to learn.
   
  Thanks, Aubrey
   
   

                 
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Received on Mon 05 Feb 2007 12:42:01 AM PST