Final answer:
The term for the irregular break of a mineral is fracture, which differs from cleavage that represents the break along planes with weak bonds.
Step-by-step explanation:
The term for the irregular break of a mineral is fracture. While cleavage refers to minerals breaking along planes with weak chemical bonds resulting in flat surfaces, fracture describes breaks that occur on planes where no weak bonds exist, resulting in irregular surfaces.
Using a hand lens to look at the surface of a mineral helps in identifying these irregularities. Furthermore, using a light source to shine on the surface can assist in determining if a plane is a cleavage plane due to its reflective properties.