Hardness: Hardness is a measure of a mineral's resistance to scratching or abrasion. It is often determined using the Mohs hardness scale, which ranks minerals from 1 (softest) to 10 (hardest). For example, talc has a hardness of 1 and is the softest mineral, while diamond has a hardness of 10 and is the hardest known natural material.
Luster: Luster refers to the way a mineral reflects light from its surface. The luster of a mineral can be described as metallic, glassy (vitreous), pearly, silky, greasy, or dull, among other terms. Luster helps to distinguish between different minerals and is an important aspect of their appearance.
Cleavage and fracture: Cleavage describes the tendency of a mineral to break along smooth, flat surfaces that correspond to planes of weakness within its crystalline structure. Minerals with good cleavage will produce smooth, flat surfaces when broken. Fracture, on the other hand, refers to how a mineral breaks when it does not exhibit cleavage. Minerals that fracture can break in irregular, uneven, or jagged patterns. Both cleavage and fracture provide insight into the atomic arrangement and bonding within a mineral's crystal structure.
Other physical properties that are used to identify minerals include color, streak, specific gravity, crystal form, and transparency, among others.