What describes the external appearance of a mineral based on its internal arrangement of atoms?

The correct choice, which is crystal form, refers specifically to the external geometric shape or framework of a mineral that is determined by the internal arrangement of its atoms. The crystal form is a reflection of the symmetry and arrangement of the mineral's crystalline structure at the atomic level. For example, minerals like quartz or halite display distinct shapes such as hexagonal or cubic forms, which are directly related to how their atoms are organized internally.

In contrast, texture refers to the size, shape, and distribution of the minerals in a rock or the way mineral surfaces feel, which doesn't necessarily indicate the atomic arrangement. Structure generally pertains to the internal composition and bonding of a mineral, rather than the external appearance. Color, while an observable characteristic, is influenced by various factors such as impurities and light absorption, and does not provide information about the atomic arrangement. Therefore, crystal form specifically encapsulates the relationship between internal atomic structure and external appearance, making it the most accurate descriptor in this context.