In mineralogy, what does the term 'crystal structure' refer to?

The term 'crystal structure' specifically refers to the arrangement of atoms within a mineral. This internal organization defines the mineral's physical properties, including its symmetry, hardness, and cleavage patterns. Each mineral has a characteristic crystal structure that contributes to its identity and classification in mineralogy. The alignment and bonding of atoms dictate how the mineral will grow, the angles at which it forms, and how it interacts with light and other minerals.

While the external shape of a mineral specimen, how it is formed in nature, and its visual aesthetics under light are all important aspects of studying minerals, they do not define 'crystal structure.' The external shape pertains more to the overall morphology of the mineral rather than the intricate atomic arrangement, while the formation process relates to geological conditions rather than structural organization. The visual aesthetics involve surface properties and optical characteristics, which are influenced by but distinct from the internal crystal structure. Hence, tightly understanding the atomic organization is crucial for a comprehensive grasp of mineral properties and behavior.