Minerals are the naturally occurring substances that form the material of rocks. They are primarily made up of atoms from the same elements that bond together in specific patterns. Crystals of mineral forming bonds between atoms belong to the same family of minerals, or a group called a mineral series. Examples of families are the carbonates, silicates, sulfates, and oxides.
The structure and composition of a mineral is determined by its chemical composition. Every mineral is made up of a combination of two or more of the elements that make up the earths crust. The chemical bond between the elements determines the arrangement of atoms and the type of crystal structure they form. The crystal lattice of a mineral is composed of a repeating array of atoms, ions, and molecules, and the physical and chemical characteristics of a mineral is determined by the arrangement of these elements.
The crystal structure of a mineral is crucial to its identification and classification. It is important to study the structure and composition of the minerals as they are essential in differentiating the properties of each type of rock.
The structure of a mineral is based on its chemical composition. All minerals have a definite chemical composition composed of elements. Elements can be combined together in different proportions and in different combinations, to make up different minerals. All minerals are made up of atoms and molecules which together form a structure similar to a lattice, where the atoms are arranged in a repeating pattern which produces a crystal shape.
The simplest minerals are composed of two elements, such as quartz (SiO2). In this type of mineral, silicon and oxygen atoms are joined together in a repeating pattern, forming a six-sided crystal. The arrangement of the oxygen and silicon atoms produces a crystal structure that is so distinct it allows quartz to be easily identified and classified.
Minerals can also be made up of more than two elements. These types of minerals, called polymeric minerals, have a more complex crystal structure than their two element counterparts. Examples of polymeric minerals include calcite (CaCO3), dolomite (CaMg(CO3)2), and halite (NaCl). In these types of minerals, different atoms bond together to form a three-dimensional lattice in which different types of atoms can be arranged in different ways to produce a unique crystal structure.
Crystal structures of minerals vary in size and shape. The size of a minerals crystal structures can range from a few atoms to hundreds of atoms. Crystals of some minerals can form sheets, flakes, needles, plates, or even discs. The physical properties of a mineral are also determined by the type and arrangement of its crystal structure.
In addition to its structure and composition, the physical characteristics of a mineral can also give clues to its identity. A minerals colour and streak, as well as its hardness and crystal form are often used to distinguish one mineral from another. Other physical characteristics such as its texture, cleavage, fracture, specific gravity, and luster can also be used to distinguish minerals.
Minerals form the major part of both sedimentary and igneous rocks. The diversity of minerals found in rocks reflects the variety and complexity of the Earths crust. The study of minerals and their structure and composition is essential for understanding the composition, formation, and properties of rocks. By examining the structure and composition of a mineral, we can gain insight into the history of the Earth and the evolution of its surface.
