from The Century Dictionary.
- Breaking obliquely; characterized by two different cleavages in directions oblique to one another, or pertaining to a mineral (as one of the triclinic feldspars) which has this property.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adjective of or relating to plagioclase
Sorry, no etymologies found.
Both plagioclastic and orthoclastic aventurine occur at several localities in the United States.