Final answer:
The term for minerals breaking along specific planar surfaces due to their crystal structure is 'cleavage,' which is predictable and differs in number and angles of planes, whereas 'fracture' is irregular and occurs without weak chemical bonds.
Step-by-step explanation:
The tendency for minerals to break along distinct planar surfaces related to their crystal structure is known as cleavage. This property allows minerals to break in a predictable way along planes where chemical bonds are weaker, creating flat cleavage planes. Cleavage can vary in the number and angles between the planes, which is an important characteristic for identifying minerals. For instance, amphibole and pyroxene can be distinguished by their different cleavage angles. In contrast, fracture describes the irregular breakage of minerals and occurs where there are no planes of weak bonds to cause cleavage.
Differentiating between cleavage and fracture can be tricky, as minerals may show signs of both. However, cleavage planes often have a brilliant reflective quality when light is shined upon them, which can be observed with a cell phone flashlight or under direct sunlight. By carefully examining the small details on the mineral's surfaces, often with the aid of a hand lens, one can identify the subtle 'elevation' changes that indicate cleavage. This level of detail in observation is crucial in determining the mineral's characteristics and, by extension, its overall identity within geological studies.