Defining Mineral Fracture
Mineral fracture is the way a mineral breaks when it does not split along cleavage planes, which are natural planes of weakness. Fracture describes the texture and shape of a surface formed when a mineral is broken in a direction where the atomic bonds are of roughly equal strength, resulting in an irregular or non-planar break.
Section 2: How Fracture Differs from Cleavage
The key difference between fracture and cleavage lies in the mineral's internal atomic structure. Cleavage occurs along flat planes where atomic bonds are weakest, resulting in smooth, predictable breaks. In contrast, fracture happens when the chemical bonds are strong and more or less uniform in all directions, causing the mineral to break in a random, uneven, or curved manner.
Section 3: A Practical Example of Fracture
A classic example of fracture is seen in the mineral quartz. When quartz is broken, it exhibits conchoidal fracture, which produces smooth, curved surfaces similar to the inside of a clam shell. This is a distinct property that helps differentiate it from minerals like calcite, which has perfect cleavage and breaks into rhombohedrons.
Section 4: Why Is Fracture Important in Mineralogy?
Observing a mineral's fracture is a crucial diagnostic tool for geologists and hobbyists during mineral identification. For minerals that lack cleavage, fracture is one of their most defining physical properties. The specific type of fracture—such as conchoidal, fibrous, or uneven—provides valuable clues about the mineral's composition and crystal structure.