Physical Characters Cleavage(解理).-The ability of a mineral to split along one or more planes parallel to actual or possible crystal planes is called cleavage. Fracture.--The mode of breaking _in directions other than those of cleavage is the type of fracture of the mineral.It is conchoidal(贝壳状的)when it has rounded surfaces suggestive of a shell; even or uneven,when nearly plain,or rough and irregular; Physical Characters  Fracture.--The mode of breaking in directions other than those of cleavage is the type of fracture of the mineral. It is conchoidal( 贝壳状的 ) when it has rounded surfaces suggestive of a shell; even or uneven, when nearly plain, or rough and irregular; Cleavage(解理).--The ability of a mineral to split along one or more planes parallel to actual or possible crystal planes is called cleavage