A mineral1 is an element2 or chemical compound3 that is normally crystalline and that has been formed as a result of geological processes. Examples include quartz4, feldspar5 minerals, calcite6, sulfur and the clay7 minerals such as kaolinite8 and smectite9.
Minerals are often used in the production of ceramics.
Properties of minerals
Minerals have a characteristic chemical composition and a highly ordered atomic structure10.
Minerals can be readily identified by several physical properties such as hardness, lustre11, streak12 and cleavage13. For example, the mineral talc is very soft and easily scratched whereas the mineral quartz is quite hard and not so easily scratched.
Crystal structure
Careful observation of crystal shapes is one of the best ways to classify and distinguish between different minerals.
A crystalline solid is made up of an orderly repeating pattern of constituent atoms, molecules14 or ions15 extending in all three spatial dimensions.
A limited number of crystal shapes have been found in nature. There are only 7 groups, or crystal systems, into which all naturally occurring crystals can be placed.
Rocks and minerals
A rock is an aggregate16 of minerals and need not have a specific chemical composition. Some rocks are predominantly composed of just one mineral. For example, limestone is a sedimentary17 rock composed almost entirely of the mineral calcite.
Other rocks contain many minerals, and the specific minerals in a rock can vary widely. Granite18 is mainly made up of feldspar minerals, quartz and mica.
When the feldspar minerals present in rock are subjected to weathering19, they break down to form clay minerals such as kaolinite (the principal mineral in kaolin20 clay) and smectite (the principal mineral in bentonite21 clay).
Ores – mineral rich rocks
Rocks from which minerals are mined for economic purposes are referred to as ores22. For example, at the Martha mine in Waihī, the ore23 body is quartz rock that has small amounts of silver24 and gold embedded in it. The ore is mined, crushed and treated chemically to release the gold25 and silver present.
Open pit mine at Waihī
The giant open pit of the Martha gold mine at Waihī in New Zealand’s North Island. Waihī still produces more gold than anywhere else in New Zealand but most of the workings are now underground. This open pit mine is one of the only such mines in the middle of a populated township in the world.
Related content
Explore the rock cycle further. Use these articles to find out more about the origins of limestone, what is clay, bone and tooth minerals and Hydroxyapatite as a bioceramic.
Activity ideas
Try these activities below, they have been developed to highlight some of the science ideas and concepts and focus on the structure, properties and classification26 of matter27.
- Minerals present in granite: identify the main minerals present in granite and investigate some of their properties.
- Measuring the specific gravity of quartz: measure the specific gravity28 of a sample of the mineral quartz.
- Crystal systems: investigate crystal shapes and crystal systems. Traditional ceramics are clay-based – clays have a mineral composition and minerals have a crystalline structure.
- mineral: 1. (Geology) A naturally occurring solid formed through geological processes. Any given mineral has a characteristic chemical composition and a specific set of physical properties. 2. (Dietary) An inorganic compound needed for proper body function and maintenance of health, for example, iron in the form of haeme present in red meat.
- element: A substance made of atoms that all have the same atomic number. Elements cannot be split into simpler substances using normal chemical methods.
- compound: A pure substance made up of two or more different elements chemically combined.
- quartz: A very commonly occurring mineral made up of a network of tetrahedrally bonded silicon and oxygen atoms.
- feldspar: Any of a group of rock-forming minerals that make up a large proportion of the Earth’s crust.
- calcite: The most common and most stable mineral form of calcium carbonate (CaCO3). It is the main component of chalk, limestone and marble.
- clay: A naturally occurring fine-grained material formed from the chemical weathering of feldspar minerals found in rocks.
- kaolinite: A clay mineral derived from the chemical weathering of feldspar minerals found in rocks such as granite.
- smectites: A family of clay minerals that includes montmorillonite and bentonite.
- atomic structure: The way in which atoms are arranged in a molecule
- lustre: The way light interacts with the surface of a mineral. For example, if the mineral has a polished metal appearance, its lustre is described as ‘metallic’. Terms like dull, greasy, waxy, pearly and adamantine (diamond) are used to describe lustre.
- streak: The colour of a crushed mineral’s powder, which may be different from the colour of the mineral. For example, calcite has a white streak even though the mineral has various coloured forms.
- cleavage: A mineral is said to have cleavage if part of the crystal breaks when forcibly hit and the broken piece retains the crystal shape. A mineral that never produces any crystallised fragments when broken off by hitting has no cleavage.
- molecule: Two or more atoms bonded together. The molecule of an element has all its atoms the same. The molecule of a compound has two or more different atoms.
- ion: An atom or group of atoms that has gained or lost electrons and has an electrical charge.
- aggregate: A collection of items gathered together to form a total quantity, for example, soil clumps together to form aggregates. Small aggregates can clump together to form larger aggregates called peds.
- sedimentary: A type of rock formed after the deposition, compaction and cementation of sedimentary material produced by either the weathering and erosion of the Earth’s surface, biological organisms (shells) or chemical precipitation (ooids). Examples of sedimentary rocks are sandstone, mudstone, limestone and coal.
- granite: A common type of crystalline igneous rock that is rich in the minerals quartz, mica and feldspars.
- weathering: Chemical, mechanical (including freezing and thawing) and biological processes that break down rocks into smaller pieces. Weathering does not include the transport away of broken-down material.
- kaolin: A white clay mainly made up of the mineral kaolinite. It is used extensively in the production of ceramics.
- bentonite: A type of clay that is rich in the mineral montmorillonite, generally formed from the weathering of volcanic ash.
- ore: Rock or sediment from which we can extract elements and minerals.
- ore: Rock or sediment from which we can extract elements and minerals.
- silver: A transition metal in Group 11 of the periodic table – symbol Ag, atomic number 47.
- gold: A transition metal in Group 11 of the periodic table – symbol Au, atomic number 79.
- classification: To arrange or organise by a set of chosen characteristics. In biology, the process of ordering living things into a system that allows scientists to identify them. Modern science uses the Linnaean system of classification where organisms are grouped based on what species they are most closely related to. In soil science, the grouping of soils with a similar range of chemical, physical and biological properties into units that can be geo-referenced and mapped.
- matter: The basic structural component of all things that have mass and volume.
- gravity: The force attracting something towards the centre of Earth (or other large mass, like a moon or planet) – the reason that things fall to Earth.
