Hi Michael, Look up "dreikanter". These are ventifacts, rocks faceted by
wind (and sand). Common in many of earth's dry locations. (deserts and
glacial). Will Estavillo

http://www.kristallin.de/wek/windkanter.htm

I looked up "dreikanter". Those are great pictures of ventifacts.
Maybe there is a wind polishing effect going on here. However, I
think I agree more with George that the shapes are more a result of
shock and blasting.

What is columnar jointing?

Michael
Mars Fossils, Pseudofossils and Problematica
http://aix1.uottawa.ca/~weinberg/mars