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Re: tektite / impactite



In a message dated 04/11/99 03:52:56 GMT Standard Time, Impactika@aol.com 
writes:

<< Since the list is (relatively) quiet and the last subject of discussion 
was 
 Tektites, may I ask a question:
 Could any of you give me a precise, clear-cut definition of "Tektite" and 
 "Impactite", and the exact difference between the 2.   >>

Hi Anne & List,

I was reading Guy Heinen's book "tektites - witnesses of cosmic catastrophes" 
late last night which gave a comparison between impact glasses and tektites 
(not including the layered, Muong Nong types). I don't have the book with me 
right now so I'm working on memory, but it goes something like this......

# Both impact glasses & tektites are products of a high energy impact event 
but the two differ greatly in the following ways:
# Water content is ~10 times higher in impact glasses than that found in 
tektites.
# The gas bubble pressure within tektites corresponds to an altitude of up to 
70km, whereas the gas pressure of impact glass is at surface level.
# Tektites are formed from the upper rock layers and mineral inclusions are 
rare - impact glasses are formed from much deeper rock layers and mineral 
inclusions are common.
# The meteoritic content within impact glass is far higher than that found in 
tektites.
# Tektites are found in distinct strewnfields away from the crater, whereas 
impact glasses are found nearby, distributed around and within the crater.
# All (almost all?) impact craters produce impact glass - only 4 impact 
craters have been shown to produced tektites.
# Impact glasses are irregular without aerodynamic shapes - tektites are more 
regular and aerodynamic shapes are common, suggesting that tektites have 
flown and ablated during high speed atmospheric passage.

That's about all I can remember....apologies for any errors! Maybe one of our 
tektite buffs can expand/add/correct some of these points?

Cheers,
Rob Elliott.

Fernlea Meteorites
http://hometown.aol.com/fernlea4/forsale.html
Milton of Balgonie,
Fife. KY7 6PY
United Kingdom
Tel: +44-(0)1592-751563
Fax: +44-(0)1592-751060
Email: FERNLEA4@aol.com

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