type 7 chondrite - According to the authors,
this is a chondrite that has experienced thermal metamorphism so great
it has been partly melted. This is a bit of an oxymoron, as such
a meteorite probably should be called an achondrite. For instance,
there are no type 7 enstatite chondrites because we call these enstatite
achondrites (aubrites) instead. Some ordinary chondrites previously
classified as type 7 are now believed to be partial impact-melts, and a
type 7 assignment (which by convention is supposed to refer to thermal
metamorphism and aqueous alteration) for such a heavily shocked chondrite
is improper. There are classes of meteorites (winonaites, acapulcoites,
lodranites), known as "primitive achondrites", that do appear to
straddle the metamorphic/igneous boundary, but they were derived from parent
bodies with oxidation states between enstatite and ordinary chondrites.