Pyrite has cubic cleavage, meaning it breaks along planes that are parallel to the faces of a cube. This cleavage is often poorly developed or indistinct, making it difficult to see in hand specimens.

Here's why:

* Pyrite's crystal structure: The cubic crystal structure of pyrite contributes to its cubic cleavage.

* Fracture: Pyrite often exhibits conchoidal fracture (smooth, curved surfaces like broken glass) which can be more prominent than its cleavage.

* Hardness: Pyrite's relatively high hardness (6.0-6.5 on the Mohs scale) makes it difficult to cleave.

Despite its often subtle cleavage, it's important to note that pyrite does possess this characteristic. Understanding cleavage patterns can be helpful in identifying minerals and understanding their properties.