1. Chemical Composition:
* Elements: Minerals are made up of one or more elements. For example, diamond is made entirely of carbon, while quartz is made of silicon and oxygen.
* Anions: Minerals are categorized by the dominant anion (negatively charged ion) present. Some examples include:
* Oxides: Minerals containing oxygen as the dominant anion (e.g., hematite, Fe2O3)
* Sulfides: Minerals containing sulfur as the dominant anion (e.g., pyrite, FeS2)
* Carbonates: Minerals containing the carbonate anion (CO3)2- (e.g., calcite, CaCO3)
* Silicates: Minerals containing the silicate anion (SiO4)4- (e.g., olivine, (Mg,Fe)2SiO4)
2. Crystal Structure:
* Arrangement of Atoms: The atoms within a mineral are arranged in a highly ordered, repeating pattern. This arrangement is known as the crystal structure.
* Symmetry: The crystal structure exhibits specific symmetries, such as rotations, reflections, and inversions.
* Unit Cell: The smallest repeating unit of the crystal structure.
How these factors work together:
* The chemical composition dictates the type of atoms and their bonding within the mineral.
* The crystal structure is a consequence of the chemical composition and bonding.
Examples of Classification:
* Feldspar Group: This group of silicate minerals is characterized by a common crystal structure and a chemical composition involving aluminum, silicon, and oxygen, with varying amounts of potassium, sodium, or calcium.
* Quartz Group: This group of silicate minerals is defined by a specific crystal structure and a chemical composition of silicon and oxygen (SiO2).
Important Note: While chemical composition and crystal structure are the primary classification criteria, other factors like physical properties (color, hardness, streak, cleavage, etc.) are also used to identify and distinguish different minerals.
