Click on the nearest side of this piece of orthoclase to hit it with a hammer and see the resultant perpendicular cleavage breaks!
Orthoclase - a potassium feldspar mineral which comes in a wide variety of colors - has one perfect cleavage plane and one good cleavage plane, perpendicular to each other.1
Reference
1. Johnsen, Ole. Minerals of the World. Princeton University Press. Printed in Hong Kong. 2010.