Geology: Igneous, Sedimentary, and Metamorphic Rocks and Minerals

A comprehensive vocabulary review of geology lecture notes covering rock classes, textures, compositions, mineral types, and sedimentary depositional environments.

Magma

Molten rock found beneath the Earth's surface.

Lava

Molten rock found at the Earth's surface.

Partial Melting

The process where rock is partially melted, producing a melt chemistry that is more felsic than the original chemistry of the rock.

Biochemical Sedimentary Rock

A sedimentary rock formed from the cemented shells of marine organisms.

Protolith

A preexisting rock that is subsequently altered to form a metamorphic rock; it may belong to any of the three primary rock types.

Foliation

A metamorphic rock texture that develops when elongated crystals align parallel with each other under the application of differential stress.

Silicates

The most common mineral group in Earth's crust, made up of silicon and oxygen bonded together (example: quartz).

Halides

Minerals formed when a metal bonds with a halogen element like chlorine or fluorine (example: halite).

Oxides

Compounds where a metal bonds directly with oxygen (example: hematite).

Sulfates

Minerals that contain a combination of sulfur and oxygen attached to a metal (example: gypsum).

Carbonates

Minerals composed of a carbon and oxygen group bonded with a metallic element (example: calcite).

Sulfides

Minerals formed when a metal bonds directly with sulfur without containing any oxygen (example: pyrite).

Bowen's Reaction Series

A series developed by Norman Bowen through cooling magma experiments showing the order in which minerals form at different temperatures as magma cools.

Igneous Rock

A type of rock that forms from the freezing of magma.

Glassy Texture

An igneous rock texture that looks like glass.

Aphanitic Texture

An igneous rock texture characterized by crystals too small to see with an unaided eye.

Phaneritic Texture

An igneous rock texture featuring crystals large enough to see that are all about the same size.

Porphyritic Texture

An igneous rock texture containing crystals large enough to see that occur in two different sizes.

Ultramafic

An igneous rock composition that is dark in color and contains $38\text{--}44\%$ $SiO_2$.

Mafic

An igneous rock composition that is dark in color and contains $45\text{--}57\%$ $Si_2$.

Intermediate (Igneous Composition)

An igneous rock composition that is intermediate in color and contains $67\text{--}76\%$ $SiO_2$.

Felsic

An igneous rock or magma composition with the highest amount of silica ($52\text{--}66\%$ $SiO_2$) and light in color.

Alluvial Environment

A depositional environment where sediment is deposited by flowing water usually originating from mountains or hills, yielding gravel, sand, and conglomerate.

Fluvial Environment

A depositional environment where sediment is deposited by rivers and streams, yielding sand, silt, clay, and sandstone.

Aeolian Environment

A depositional environment where sediment is deposited by wind, usually in deserts or sand dunes, producing well-sorted sand and sandstone.

Lacustrine Environment

A depositional environment where sediment is deposited in lakes, yielding fine sand, silt, clay, shale, and sometimes sandstone.

Deltaic Environment

A depositional environment formed where a river enters a lake or ocean, depositing sand, silt, clay, and sandstone.

Lagoonal Environment

A depositional environment consisting of shallow water separated from the ocean by a barrier, accumulating mud, clay, shale, and limestone.

Shelf/Platform Environment

A shallow ocean water depositional environment characterized by limestone, sandstone, shale, and fossils.

Abyssal Plain Environment

A deep ocean floor depositional environment where fine mud, clay, and shale are deposited.

Sedimentary Rock

Rock formed by weathering, erosion, deposition, compaction, and cementation of deposits of preexisting rocks and once-living organisms above the surface.

Weathering

The process of disintegrating rocks, occurring as either physical weathering or chemical weathering.

Lithification

The process that turns sediments into solid rock through compaction and cementation of grains.

Sedimentary Structures

Features in sedimentary rocks that provide clues about the environment in which deposition occurred.