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Tektite textures
Bob King wrote:
> I have always wondered what the cause is of their fascinating texture,
> ie. the small circular pits and the numerous wormlike tracks. Are they
> from erosion or do they represent some kind of outgassing?
V.E. Barnes, 1961, Tektites, Sci.Am. 205, 58-65:
Barnes mentions flow patterns, strain patterns, fused quartz particles
in tektites, and "fingers" in australites.
1) Flow pattern: " ... within a tektite shows that the glass is made up
of many layers having different composition. The distinctness of the
patterns shows that the tektite cooled quickly".
2) Strain pattern: " ... within a tektite shows up plainly when the
tektite is placed between two crossed polarizing sheets. The [pictured]
pattern shows that the tektite is the same size as when it was formed".
3) Fused quartz particles: " ... are the white, apparently raised areas
seen [in the photo] here in the thin section of a tektite. The black
dots are vacuum bubbles".
4) "Fingers" in australites: " ... are rich in silica. This indicates
that very high temperature of formation caused other constituents to
evaporate. The tiny black dots within the fingers are even richer in
silica than the surrounding area".
Regards,
Bernd
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