Minerals

• A mineral is a naturally occurring solid substance with a defined chemical composition and crystalline structure.

• Minerals may consist of a single type of atom or they may contain two or more different types of atoms in a fixed arrangement.

• In other words, minerals may be elements or compounds.

• Examples of minerals that are elements include sulfur, gold and diamond.

• Examples of minerals that are compounds include quartz, calcite and halite.

• Minerals that are compounds are named differently to the chemical compounds they are composed of. There are several reasons for this.

• Firstly, it distinguishes minerals as naturally occurring forms of chemical compounds.

• For example, the mineral quartz is a naturally occurring form of the compound silicon dioxide (SiO₂).

• Secondly, some compounds occur naturally with different crystal structures.

• For example, stishovite is also a mineral form of silicon dioxide, but with a different crystal structure to quartz.

• Thirdly, many minerals have complex molecular structures, where the types of atoms within them can vary.

• For example, the mineral olivine has a variable composition represented by the general molecular formula (Mg,Fe)₂SiO₄. This formula shows that the proportions of magnesium (Mg) and iron (Fe) can vary.

Rocks are composed of minerals, which are naturally occurring elements or compounds with a crystalline structure.

(Images: James St. John, Wikimedia Commons; Romaine, Wikimedia Commons; James St. John, Wikimedia Commons; Kritzolina, Wikimedia Commons)