Cleavages are well developed and commonly seen in specimens in rocks.
The third direction fractures, however, and has an irregular, broken appearance. The fracture surface is the top surface in this picture, but note the cleavage face on the right side. The surface is typically transluscent, that is, light seems to penetrate below the surface so you can see into the mineral. Na Plagioclase is common. In intermediate igneous rocks plagioclase becomes more calcium rich but the color tends to remain white or light gray.