Sperrylite has a poor cleavage, and its polished surface has a metallic lustre.
2.
Sodalite's six directions of poor cleavage may be seen as incipient cracks running through the stone.
3.
Zorite has perfect cleavage along the planes { 010 } and { 001 }, while having poor cleavage along the plane { 110 }.
4.
Minerals with many cleavages might not break equally well in all of the directions; for example, calcite has good cleavage in three direction, but gypsum has perfect cleavage in one direction, and poor cleavage in two other directions.
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