For example, quartz may be found in almost any color, but its streak is always white. Cleavage is the splitting of a mineral in definite directions because of the internal structure of the crystals present. Most minerals break along a certain plane. Mica cleaves into thin sheets. Galena breaks into little cubes.
Minerals also break without cleavage or across cleavage planes.
These characteristic fractures are also helpful in mineral identification. Quartz and malachite fracture with shell-like curves. Native metals often break leaving jagged edges. Some properties, such as magnetism and luminescence, are not present in all minerals but can be useful in identifying certain minerals or mineral groups. Some minerals have a unique texture, odor, or taste.