Fracture (mineralogy)

Five types of fractures are recognized in mineralogy: conchoidal, earthy, hackly, splintery (or fibrous), and uneven factures.

Conchoidal fracture breakage that resembles the concentric ripples of a mussel shell.

Note that obsidian is an igneous rock, not a mineral, but it does illustrate conchoidal fracture well.

It is frequently seen in relatively soft, loosely bound minerals, such as limonite, kaolinite and aluminite.

It occurs in a wide range of minerals including arsenopyrite, pyrite and magnetite.