Plagioclase cleavage rhomb

This is not a crystal of plagioclase, but rather, a cleavage rhomb. As such it displays the three cleavage planes (orientations) that are one of the diagnostic proerties of plagioclase. Two cleavages which intersect at ~90° are prominent, while the third cleavage is weaker and intersects the second at a lower angle. The latter cleavage orientation is difficult to spot in most specimens.