Final answer:
A mineral's cleavage or fracture describes how it breaks, with cleavage meaning flat, predictable breaks and fracture indicating irregular breaks. These properties are key in determining a mineral's identity and understanding its geological history.
Step-by-step explanation:
The characteristic way a mineral breaks is described by its cleavage or fracture. Cleavage refers to the tendency of a mineral to break along flat planes where atomic bonds are weaker, resulting in smooth, flat surfaces that reflect light uniformly. When minerals display irregular or uneven breaks without any pattern due to the absence of weak bonds, the term used is fracture. This property helps in identifying minerals and understanding their crystal structure and chemical composition. For example, knowing whether a rock contains amphibole or pyroxene through their different cleavage can provide insights into the rock's geologic history.
Additionally, the hardness of a mineral, which determines how easily it can be scratched, impacts its fracture and cleavage characteristics. Hardness is an essential property for field identification and helps distinguish between minerals in identifying and classifying them.