Rocks and Minerals
Elementary School
Definition
Naturally occurring solid materials of the Earth. Minerals are pure substances with a definite composition and structure, while rocks are made of one or more minerals combined together.
Worked examples
Quartz is a mineral made of silicon and oxygen in a fixed ratio; granite is a rock containing quartz, feldspar, and mica minerals.
A mineral has one definite composition; a rock is a mixture of different minerals.
Halite (table salt) is a mineral with the formula \(\)NaCl\(\); sandstone is a rock made of cemented sand grains.
Halite's composition never changes; sandstone's mix of minerals can vary from sample to sample.
Common mistakes
- calling any hard Earth material a 'rock' → distinguishing minerals (pure substances) from rocks (mixtures) A mineral has a definite chemical formula; a rock is an aggregate of one or more minerals.
- thinking all rocks contain multiple minerals → some rocks are made of just one mineral (e.g., limestone from calcite) Rocks can be monomineralic or polymineralic depending on how they formed.
- assuming minerals must be shiny or colorful crystals → minerals include dull or earthy forms like clay and graphite Crystal habit and luster vary widely; a mineral is defined by composition and structure, not appearance alone.
Where you'll use it next
You'll use this distinction when studying the rock cycle, identifying rock types (igneous, sedimentary, metamorphic), and understanding Earth's crust composition in geology and environmental science.
See also
Reviewed by Pat Cheng, M.Ed. — StudyPug Curriculum Lead · Last updated June 6, 2026