A mineral's tendency to break along flat, reflective surfaces is known as cleavage. This property is identified by the way a surface reflects light and is crucial for distinguishing minerals like amphibole from pyroxene. Cleavage and fracture are key factors in understanding a mineral's physical characteristics and its geological history.
A mineral's tendency to break along bright, reflective planar surfaces is called cleavage. Cleavage occurs when minerals break along planes where chemical bonds are weak, creating flat surfaces known as cleavage planes. These planes can vary in number and angles if there are more than one. The examination of cleavage is essential in identifying minerals, as it helps differentiate minerals with similar physical properties but different geological origins, like amphibole and pyroxene. To identify cleavage, one could shine a light on the mineral's surface using tools like a cell phone flashlight or sunlight. A brilliant reflection typically indicates a cleavage plane.
It is important to note that minerals can also show fracture, an irregular breakage that occurs where no weak bonds are present, leading to uneven surfaces. Fracturing can sometimes occur along cleavage planes, which complicates identification. Thus, careful examination with a hand lens for subtle changes in the surface height is often necessary to discern cleavage.
Understanding mineral cleavage is not only crucial for identifying minerals but also for revealing information about the geological history of the rocks in which they are found. The physical properties of cleavage can influence the overall texture and behavior of a mineral, including its brittleness and insulating properties. This examination often involves looking for changes in 'elevation' on the surface that indicate cleavage planes.