Here's why:
* Minerals are naturally occurring, solid substances with a defined chemical composition and a specific crystalline structure. This means the arrangement of atoms within the mineral is also important, but the chemical makeup is the primary defining factor.
* Different chemical compositions result in different properties. These properties include things like:
* Hardness: How resistant a mineral is to scratching.
* Cleavage: The tendency of a mineral to break along specific planes.
* Fracture: How a mineral breaks when it doesn't cleave.
* Luster: The way a mineral reflects light.
* Color: The way a mineral absorbs and reflects light.
* Streak: The color of the powder a mineral leaves when rubbed on a streak plate.
* Density: The mass of a mineral per unit volume.
* Crystal habit: The typical shape a mineral grows in.
Example: Quartz is a mineral with the chemical formula SiO2 (silicon dioxide). Feldspars are another class of minerals with a more complex formula, typically including aluminum, silicon, oxygen, sodium, potassium, and calcium. The difference in their chemical composition leads to different properties and allows geologists to easily distinguish between them.
Note: While chemical composition is the primary characteristic, geologists also use other factors like crystal structure, formation process, and physical properties for further classification and identification.
