1. Hardness: The strength of the chemical bonds between atoms within a mineral determines its resistance to scratching. Stronger bonds, such as those in diamond (covalent bonds), result in higher hardness. Weaker bonds, like those in talc (ionic bonds), lead to lower hardness.
2. Cleavage: This refers to the tendency of a mineral to break along specific planes of weakness. These planes often correspond to areas where the chemical bonds are weaker, allowing the mineral to cleave cleanly. For example, the strong ionic bonds in halite (NaCl) make it cleave along cubic planes.
