There are two physical properties of minerals that both result in smooth, flat surfaces with specific angles between them. The first property is externally visible and is the result of how the mineral forms; the second is inherently internal and is the result of breaking a sample of the mineral. These properties are called:.
1. hardness and cleavage.
2. cleavage and hardness.
3. crystal habit and cleavage.
4. cleavage and crystal habit.

3. crystal habit and cleavage.

Explanation:

Crystal habit is a distinctive characteristic which is shown in its general shape,  crystallographic forms, how developed each form is.

Cleavage is the ability of a mineral to break in smooth planes parallel to zones of weak bonding. Cleavage in three directions at right angles (90o). Cubic cleavage. Cleavage in three directions not at right angles (120o and 60o).

astronomers such as edwin hubble.