[meteorite-list] Diogenite Distinctions....was List of meteorites from Vesta?

[MEM]

<<Dunite is the "Earth version" of Tatahouine.>>

Sorry, well.... but not exactly. Orthopyroxene is close elementally but 
chemically a different class of silicate mineral.  Pyroxene isn't the same as 
dunite--aka olivine rock.  There is an axiom in mineralogy :" color is the list 
reliable characteristic for identification".  Pyroxene forms when the available 
oxygen is less than optimal (as in Olivine)so it has to stack differently to 
double up on oxygen bonds.

How-so-ever, there is at least one NWA achondrite described as "Dunite with HED 
affinities" yet the same literature keeps talking about "olivine diogenites".  
What level of  olivine content switches  from Olivine Dio over to a Dunite Dio?

Perhaps the use of "dunite" in the literature is more inline with the trend to 
describe achondrites in terms of rock-type/rock fabric, than traditional 
composition-based schemes.  Remember the old days of Olivine, Bronzites, and 
Amphoterites  instead of H, L and LL?

Elton