[meteorite-list] BO - Barred Olivine Chondrule: RFS Picture of the Day

[bernd.pauli at paulinet.de]

Walter wrote: "Thanks Michael - thank you Andi and John"

Yes, thanks a lot ... that's a beautiful barred olivine chondrule! 

"Okay, I admit I know nothing about thin sections. Someone educate me."

Woe, it's me, shame and scandal in the family ... :-))

"What are the vertical pieces that sort of remind me of mitochondria in a cell?"

These worm-like or larva-like features are olivine bars - hence BO chondrule,
barred olivine chondrule. Well, a similar picture can be seen in O.R. Norton's
Cambridge Encyclopedia, page 113.

"What does the horizontal color gradient indicate?"

This may indicate three things:

1) in accordance with what O.R. Norton says on p. 113, the rim and the
   bars on the right are not in optical continuity (not oriented identically);

2) the bars and the rim on the left are chemically somewhat different,
   probably richer in iron than the yellow-orange crystals on the right;

3) the thin section does not have a uniform thickness.

(1) and (3) are improbable as both bars and rim seem to be oriented
identically (north - south in the picture), so my guess is that the color
gradient indicates chemical composition as explained in (2).

Best TS wishes,

Bernd