Minerals are any natural crystalline solid with a specific chemical formula. For example, quartz is a mineral formed by the combination of silicon and oxygen with the formula SiO2.
Rocks are solid masses, formed by the mixture of minerals that maintain their composition. For example, granite is a rock made up of different proportions of quartz, feldspar, and mica minerals.
Both minerals and rocks are part of the earth’s crust. Minerals are extracted from the rocks for a variety of uses.
|Definition||Natural inorganic solid with ordered internal structure and defined chemical composition||Any solid mass of mineral matter|
Crystals of combinations of oxygen, silicon, aluminum, iron, calcium, sodium, potassium and magnesium.
|formation process||Crystallization||Fusion |
|Igneous rocks |
Limestone: Composed of the mineral calcite.
Marble: limestone metamorphic rock.
Salt rock: sedimentary rock composed of halite.
Sandstone: sedimentary rock composed of fragments of quartz and other minerals.
Basalt: igneous rock composed of silicates of magnesium and iron.
Granite: igneous rock made up of quartz, mica, and feldspar.
Serpentinite: metamorphic rock composed of olivine, pyroxene, and chromite
Quartzite: sandstone metamorphic rock.
Obsidian: glassy volcanic rock.
Examples of minerals: galena (lead sulfide), olivine (magnesium/iron silicate), quartz (silicon dioxide), and corundum (aluminum oxide).
In geology, a mineral is a naturally occurring inorganic solid that has a defined chemical structure that gives it a unique set of physical properties. Some materials produced by humans, such as steel, are not considered minerals.
Minerals are formed through the process of crystallization. This process consists of the chemical union of molecules or ions to build an ordered and repetitive structure. For example, silicate minerals form tetrahedra, while halite forms cubes.
There are minerals with the same composition with different crystalline forms. Calcium carbonate can form the mineral calcite, with a trigonal crystal system. Instead, aragonite is the mineral found in pearls and the shells of some marine animals, with an orthorhombic crystal system.
Physical properties of minerals
The physical properties of minerals allow us to identify them:
Primary Properties: Crystalline form, gloss, color, streak, hardness, cleavage, and specific gravity.
Secondary properties: magnetism, taste, touch, smell, elasticity, malleability, bi-refraction and chemical reaction with hydrochloric acid.
Mineral groups and examples
Almost 4000 minerals are known on Earth, a fraction of them are known as rock-forming minerals. Just eight elements make up most of those minerals: oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium.
Depending on their composition, minerals are classified into the following groups:
Silicates: contain the elements oxygen and silicon, forming tetrahedrons, such as quartz, olivine (magnesium/iron silicate), augite, biotite and garnet.
Carbonates: Composed of the carbonate ion such as calcite and dolomite.
Halides: they are formed by anions of halogen elements (chlorine, fluorine, bromine and iodine), such as halite, fluorite and sylvine.
Oxides: contain the oxygen anion bound to one or more positive ions or cations, such as hematite, magnetite, and corundum.
Sulfides: sulfur compounds with other metals such as galena (lead sulfide), pyrite (iron sulfide), chalcopyrite (copper sulfide), cinnabar (mercury sulfide).
Sulfates: sulfate anion compound such as gypsum and barite.
Native elements: minerals made up of a single element, such as gold, copper, diamond (made of carbon), sulfur, silver, and platinum.
Examples of rocks: marble (metamorphic rock), sandstone (sedimentary rock), basalt (igneous rock), and serpentinite (metamorphic rock).
Rocks are conglomerates of various materials, most of them made up of various minerals that maintain their properties. An exception is the sedimentary rock limestone, which is made up of the mineral calcite.
Some rocks, such as obsidian and pumice, are not made up of minerals. These are volcanic rocks of non-crystalline glassy substances. Carbon is the remains of solid organic compounds.
The process of rock formation is varied. Volcanic or igneous rocks are formed by the fusion process of underground material and the solidification of magma and lava. Sedimentary rocks are formed by deposition and compaction. And by pressure and temperature metamorphic rocks are formed.
Types of rocks with examples
Igneous rocks: they are composed almost entirely of silicate minerals. Examples of igneous rocks are diorite, andesite, and basalt.
Sedimentary rocks: they are derived from sediments that are cemented. Examples of sedimentary rocks are sandstone, shale, limestone, and coal.
Metamorphic rocks: they are formed by great pressures and high temperatures on other rocks. Examples are marble, gneiss and quartzite.
You may also be interested in seeing: