from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Geology Having right-angled cleavage.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Having cleavage planes at right angles; as in orthoclase.
from the GNU version of the Collaborative International Dictionary of English
- adj. Breaking in directions at right angles to each other; -- said of the monoclinic feldspars.
from The Century Dictionary and Cyclopedia
- Characterized by cleavages at right angles to one another: said of certain species of the feldspar group, particularly orthoclase; pertaining to such species, or specifically to orthoclase.
Both plagioclastic and orthoclastic aventurine occur at several localities in the United States.