Rocks and Minerals

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Rock Noun

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[rok]

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Rock

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A naturally formed, non-living Earth material made of collections of mineral grains held together in a firm, solid mass.

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Example: This diagram illustrates the rock cycle, showing how rocks transform between igneous, sedimentary, and metamorphic types through processes like melting, cooling, and pressure.

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Mineral Noun

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[min-er-uhl]

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Mineral

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A naturally-occurring, inorganic, homogeneous solid with a definite chemical composition and an ordered internal structure.

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Example: This image shows quartz crystals. Minerals are solids with a specific chemical makeup and an orderly internal structure, which creates flat-faced crystal shapes.

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Texture Noun

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[teks-cher]

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Texture

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A description of the size, shape, and arrangement of mineral grains that constitute a rock.

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Example: This image shows a volcanic rock's texture, which is defined by its parts: large crystals (phenocrysts), gas bubbles (vesicles), and the fine-grained groundmass.

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Crystal Noun

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[kris-tl]

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Crystal

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A solid material whose constituent atoms are arranged in a highly ordered, repeating geometric pattern.

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Example: This image shows a geode, a hollow rock lined with crystals, which are solid materials with atoms arranged in a highly ordered, repeating pattern.

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Inorganic Adjective

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[in-or-gan-ik]

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Inorganic

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Relating to or denoting substances that are not derived from living matter and do not contain carbon.

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Example: This image shows the organized, repeating crystal lattice structure common in many inorganic minerals, which are substances not derived from living matter.

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Igneous Rock Noun

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[ig-nee-uhs rok]

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Igneous Rock

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A type of rock formed through the cooling and solidification of magma or lava from a molten state.

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Example: This image shows a piece of igneous rock, pointing out key features like vesicles (gas bubbles), phenocrysts (large crystals), and the fine-grained groundmass.

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Sedimentary Rock Noun

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[sed-uh-men-tuh-ree rok]

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Sedimentary Rock

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A type of rock formed from the compaction and cementation of small pieces of material called sediments.

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Example: This diagram shows how loose sediments are squeezed together (compaction) and then glued by minerals (cementation) to form a solid sedimentary rock over time.

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Metamorphic Rock Noun

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[met-uh-mawr-fik rok]

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Metamorphic Rock

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A rock that has been transformed into a different kind of rock by great heat and pressure.

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Example: This diagram shows how hot magma inside the Earth bakes the surrounding rock, changing it into metamorphic rock through a process called contact metamorphism.

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Magma Noun

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[mag-muh]

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Magma

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Extremely hot, molten rock that is located deep beneath the surface of the Earth, containing dissolved gases.

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Example: This diagram shows that magma is molten rock stored in a magma chamber beneath the Earth's crust before it erupts from a volcano.

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Lava Noun

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[lah-vuh]

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Lava

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Molten rock that has been expelled from the interior of a planet during an eruption onto the surface.

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Example: This diagram shows that lava is molten rock that flows out onto the Earth's surface from a volcano, distinguishing it from magma which is underground.