Final answer:
Minerals' internal atomic structures are responsible for their hardness, cleavage, and crystal shape, which are reliably determined by the atomic arrangements and bonding.
Step-by-step explanation:
The internal atomic structure of a mineral most likely determines the mineral's hardness, cleavage, and crystal shape. The internal arrangement of atoms within a mineral provides the foundation for its physical characteristics. Minerals on the Mohs' scale, which is based on a mineral's relative ability to resist abrasion, exhibits the importance of atomic structure for hardness. The concept of cleavage, where minerals break along planes of weak chemical bonds, is a direct result of how atoms are bonded in the crystal lattice.
Furthermore, the mineral's innate tendency to form a particular crystal shape is a manifestation of the orderly, repetitive, geometric spatial arrangement of atoms. Therefore, internal atomic structures are pivotal to these three discernable mineral properties. Elements substituting one another in a mineral's atomic structure can alter characteristics such as color. However, this is not as directly correlated to the atomic structure as hardness, cleavage, and crystal shape.