Glossary

atoms (AT-uhms): the tiniest parts, or building blocks, of elements

corundum (ko-RUN-duhm): a common, colorless mineral that occasionally occurs in gemstone form

crystals (KRISS-tuhls): the solid forms of a substance, such as a mineral, containing many repeated flat surfaces

elements (EL-uh-muhnts): basic chemicals found in all matter that cannot be split into simpler substances

extrusive (ex-TRUH-siv): igneous rock that forms above ground

humus (HYOO-muhss): decaying organic matter in the soil

igneous (IG-nee-uhss): a type of rock formed when rising magma cools and hardens

intrusive (in-TRUH-siv): igneous rock that forms below ground

lava (LAH-va): magma that flows out of a volcano

magma (MAG-muh): hot, liquid rock often found deep beneath the Earth's surface in underground pockets

metamorphic (met-uh-MOR-fik): a type of rock that is created when pre-existing rock changes form due to heat and/or pressure

sediments (SED-uh-ments): particles of rock and other materials that settle, often in layers

sedimentary (sed-uh-MEN-tuh-ree): a type of rock formed by layers that are squeezed and cemented together

streak (STREEK): a long, thin smear, often referring to the powder left behind when the mineral rubs across a dull-white surface

weathering (WETH-ur-eeng): changes caused by natural forces, including rain, ice, and wind