The following is a list of rock types recognized by geologists. There is no agreed number of specific types of rock. Any unique combination of chemical composition, mineralogy, grain size, texture, or other distinguishing characteristics can describe a rock type. Additionally, different classification systems exist for each major type of rock.[1] There are three major types of rock: igneous rock, metamorphic rock, and sedimentary rock.

Igneous rocks

Main article: Igneous rock

A sample of andesite (dark groundmass) with amygdaloidal vesicles filled with zeolite. Diameter of view is 8 cm.

Sedimentary rocks

Main article: Sedimentary rock

Bituminous coal seam in West Virginia
Limey shale overlaid by limestone. Cumberland Plateau, Tennessee
Dolomite crystals from Touissite, Morocco
Turbidite (Gorgoglione Flysch), Miocene, South Italy

Metamorphic rocks

Main article: Metamorphic rock

Phyllite
Banded gneiss with a dike of granite orthogneiss
Marble
Quartzite
Manhattan Schist, from Southeastern New York
Slate

Specific varieties

The following are terms for rocks that are not petrographically or genetically distinct but are defined according to various other criteria; most are specific classes of other rocks, or altered versions of existing rocks. Some archaic and vernacular terms for rocks are also included.

See also

References

  1. ^ "BGS Rock Classification Scheme - Igneous - Metamorphic - Sedimentary - Superficial". British Geological Survey (BGS). Retrieved 2019-05-28.