What does the term "habit" refer to in mineralogy?

The term "habit" in mineralogy specifically refers to the characteristic external crystal shape or form of a mineral. This concept is crucial because the outward appearance of a mineral, including its symmetry, angles, and overall shape, is indicative of its internal structure and the conditions under which it crystallized. Each mineral has a unique habit that can help in its identification; for example, quartz may appear as elongated prisms or might have a more granular form, while calcite may exhibit rhombohedral shapes.

Understanding a mineral's habit allows geologists and gemologists to recognize it more easily among the multitude of different minerals. This characteristic can be influenced by environmental factors during its formation, such as temperature and pressure, but it is the external appearance that is classified under "habit." The other options focus on different aspects of minerals, such as their composition, formation conditions, and typical locations, but they do not define the term "habit" specifically.