Earth and Life: Rocks, Rock Cycle and Minerals

Vocabulary flashcards covering key terms about rocks, the rock cycle, minerals and their properties from the lecture notes.

Rock

Naturally occurring solid aggregate of one or more minerals, sometimes containing non-mineral particles.

Petrology

The scientific study of rocks, their origin, composition and structure.

Petrologist

A scientist who classifies and studies rocks and how they form.

Igneous rock

Rock formed when molten magma or lava cools and solidifies.

Intrusive (plutonic) igneous rock

Igneous rock that crystallizes slowly beneath Earth’s surface, producing coarse grains.

Extrusive (volcanic) igneous rock

Igneous rock that cools rapidly at the surface from lava, producing fine-grained or glassy textures.

Granite

Coarse-grained intrusive igneous rock rich in quartz and feldspar.

Diorite

Grey, intermediate intrusive igneous rock with a salt-and-pepper appearance.

Gabbro

Dark-colored mafic intrusive igneous rock composed mainly of pyroxene and plagioclase.

Basalt

Fine-grained dark extrusive igneous rock; main component of oceanic crust.

Obsidian

Black, glassy volcanic rock formed by very rapid cooling of silica-rich lava.

Pumice

Light, highly vesicular volcanic rock that can float on water.

Scoria

Vesicular, mafic volcanic rock darker and denser than pumice.

Andesite

Fine-grained extrusive rock of intermediate composition, common in stratovolcanoes.

Rhyolite

Light-colored, silica-rich extrusive igneous rock equivalent to granite.

Sedimentary rock

Rock formed from accumulation, compaction and cementation of sediments or biological material.

Weathering

Physical or chemical breakdown of rocks at Earth’s surface.

Erosion

Transport of weathered material by water, wind, ice or gravity.

Compaction

Process in which weight of overlying sediments presses and squeezes deeper layers.

Clastic sedimentary rock

Sedimentary rock made of fragments of pre-existing rocks mechanically weathered.

Conglomerate

Clastic rock composed of rounded gravel-size particles cemented together.

Breccia

Clastic rock made of angular gravel-size fragments.

Sandstone

Clastic rock made mostly of sand-size grains.

Siltstone

Fine clastic rock composed of silt-size particles.

Shale

Very fine-grained clastic rock that splits into thin layers; consists mainly of clay.

Chemical sedimentary rock

Rock formed when dissolved minerals precipitate from solution, altering chemical composition.

Rock salt

Evaporite chemical sedimentary rock composed mainly of halite.

Gypsum

Soft evaporite mineral forming chemical sedimentary rock; CaSO₄·2H₂O.

Dolostone (Dolomite)

Sedimentary rock rich in the mineral dolomite, CaMg(CO₃)₂.

Chert

Hard, microcrystalline silica chemical rock, often forming nodules.

Organic sedimentary rock

Rock formed from accumulation of plant or animal debris.

Coal

Carbon-rich organic sedimentary rock derived from compressed plant material.

Coquina

Limestone composed almost entirely of loosely cemented shell fragments.

Limestone

Sedimentary rock mainly of calcite, often originating from marine organisms.

Metamorphic rock

Rock that has been altered in the solid state by heat, pressure and/or chemically active fluids.

Metamorphism

Process that changes a parent rock’s mineralogy and texture through heat and pressure.

Foliated metamorphic rock

Metamorphic rock displaying planar bands or layers caused by directional pressure.

Non-foliated metamorphic rock

Metamorphic rock lacking banding; crystals grow without preferred orientation.

Contact metamorphism

Metamorphism produced by heat from nearby magma, producing non-foliated rocks.

Regional metamorphism

Widespread metamorphism caused by high pressure and temperature during mountain-building.

Rock cycle

Continuous series of processes in which rocks change from one type to another over geologic time.

Mineral

Naturally occurring, inorganic solid with a definite chemical composition and ordered atomic arrangement.

Mineralogy

Branch of geology that studies minerals’ properties, composition, and classification.

Mineralogist

Scientist who investigates minerals.

Luster

How a mineral reflects light; described as metallic or non-metallic.

Hardness

Resistance of a mineral to scratching, measured by the Mohs scale.

Mohs scale of hardness

Ten-point scale ranking minerals from talc (1) to diamond (10) based on scratch resistance.

Streak

Color of a mineral’s powdered form obtained by rubbing on unglazed porcelain.

Cleavage

Tendency of a mineral to break along flat planes of weakness.

Fracture

Irregular breakage of a mineral where cleavage is absent, e.g., conchoidal.

Crystal habit

Typical external shape a mineral crystal develops as it grows.

Fluorescence

Ability of some minerals to glow under ultraviolet light.

Magnetism (mineral property)

Attraction of minerals such as magnetite to a magnetic field.

Radioactivity

Emission of ionizing radiation by minerals containing unstable isotopes, e.g., uraninite.

Reactivity (acid test)

Effervescence shown by minerals like calcite when exposed to weak acid.

Silicate mineral class

Largest group of minerals built from silicon-oxygen tetrahedra.

Sulfide mineral class

Minerals consisting of sulfur combined with a metal; dense and brittle.

Oxide mineral class

Minerals where oxygen is bonded to a metal, e.g., magnetite, hematite.

Sulfate mineral class

Minerals containing the sulfate ion (SO₄)²⁻, often soft and translucent, e.g., gypsum.

Halide mineral class

Minerals formed from halogen elements and metals; often soluble, e.g., halite.

Phosphate mineral class

Minerals with PO₄ groups, often brightly colored, e.g., apatite.

Carbonate mineral class

Minerals composed of the carbonate ion (CO₃)²⁻ with metals; react with acid, e.g., dolomite.

Mineraloid

Naturally occurring substance that lacks a crystalline structure, such as amber or opal.