Dear Christian and all,
As a part-time igneous person, I must comment on the recent gross
slurr upon the noble discipline.
The terms quartz diorite, trondhjemite and tonalite are all quite
distinct rock types that have been defined in the "blue book". There
are chemical/mineralogical classification diagrams that are used to
determine which term is used for a particular sample. The names are
in no way equivalent, though a trondhjemite is a sodium-rich
leucotonalite (a very meaningful distinction, I assure you). There
does not seem to be a problem with any of these words.
Charnockite, charnoenderbite and enderbite are idiosyncratic
terms that "charnockitologists" insist on using. They actually have
better synonyms (e.g., enderbite = Opx tonalite). Although these
special terms are a bit strange, there is no ambiguity about what
Finally, despite having an accepted terminology and rules of
usage, we can never stop some individuals from misnaming things (e.g.
calling icelandite or hawaiite by the name of andesite). This is just
incorrect. It may create misunderstanding, but it does not reflect
general uncertainty over what the names really mean. We have our blue
book! The same could not be said for the world of metamorphic