[meteorite-list] meaning of breccia

[aerubin at ucla.edu]

Just a clarification of the word breccia.  A breccia is a rock that  
contains distinct chunks or clasts.  If the clasts are all of the same  
lithology and the host is the same lithology as the clasts, the rock  
is a monomict breccia.  If the clasts or hosts are from different  
meteorite groups, the rock is a polymict breccia.  Wasson coined the  
term "genomict breccia" for chondrites that have clasts from the same  
group but of different petrologic types (e.g., L5 and L6 clasts in an  
L-chondrite host). A regolith breccia is a rock from the surface of  
its parent body.  A prime example is the H-chondrite Dimmitt.  In  
addition to H4 and H5 clasts,the Dimmitt host contains some H3  
material.  There are also some carbonaceous chondrite clasts (CM and  
unspecified C3) and an LL5 clast. Regolith breccias are also typically  
rich in solar-wind-implanted rare gases and may contain mineral grains  
with solar-flare particle tracks.