1. Crystalline Structure: Minerals have a highly ordered, repeating arrangement of atoms called a crystal lattice. This gives minerals their characteristic shape, cleavage, and other physical properties.

* Example: Halite (table salt) has a cubic crystal structure, which is why salt crystals often form cubes.

2. Chemical Composition: Minerals are naturally occurring, inorganic solids with a specific chemical formula. Each mineral has a unique combination of elements.

* Example: Quartz is always composed of silicon and oxygen (SiO2).

3. Physical Properties: Minerals exhibit a variety of unique physical properties that can help identify them, including:

* Hardness: Resistance to scratching (Mohs Hardness Scale)

* Cleavage: Tendency to break along specific planes of weakness

* Fracture: How a mineral breaks when not along cleavage planes

* Color: Can be helpful, but can be misleading due to impurities

* Streak: The color of the mineral's powder

* Luster: How light reflects off the mineral's surface (metallic, glassy, etc.)

* Density: The mineral's mass per unit volume

These special properties make minerals fascinating and unique, allowing us to identify and classify them.