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MISSING: 9.04 kilogram Sikhote-Alin shrapnel individual   More Info


 
DAG 767   contributed by Andreas Ruh   MetBul Link

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Copyright (c) Andreas Ruh.
Thin section under plane polarized light.

TKW 35.8 grams. Fall not observed. Found 1999, Al Jufrah, Libya.

 


Andreas writes:
Thin section in plane polarized light. The picture shows ringwoodite in heavliy shocked L6 chondrite DaG 767 (shock stage: S6). Width of the photo: approx. 210 micrometer.
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Photo 1

Found at the arrow (green or red) on the map below

 


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Andreas Ruh
 3/1/2019 1:27:57 AM
Hello Mike, thank you for your comment. Birefringence is visible, when you observe a thin section between crossed polarizers. But this photo was taken under plane polarized light. So, we are not talking about birefringence colours but about the inherent colours of the minerals. The blue colour of ringwoodite is due to the Fe2+ content. If a ringwoodite grain is pure Mg2SiO4 then it would be colourless. But even low concentrations of Fe2SiO4 cause the blue colour. The physics behind that is not understood completely but the blue colour is thought to be due to Fe2+*Fe3+ charge transfer.
Mike Fiedler
 2/28/2019 9:04:15 PM
Really cool specimen, Andreas. I'm intrigued by the blue. Had read a little bit some time ago about Ringwoodite, but forgotten nearly everything I may have read, so I googled it. All the photos I saw have the deep blue, but as a cubic crystal, with no birefringence, how does that blue come through in a thin section?
Bernd Pauli
 2/27/2019 7:01:34 AM
Beautiful example of ringwoodite! By the way, the color of ringwoodite aggregates ranges from purple to blue and colorless.
 

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