A mineral is a pure, naturally occurring substance with a fixed chemical formula and crystal structure, while a rock is a solid mixture (aggregate) of one or more minerals stuck together.

Simple definitions

  • Mineral : A naturally occurring, inorganic solid with a definite chemical composition and an orderly, repeating internal (crystalline) structure. Quartz \text{(SiO_2)} is a classic example.
  • Rock : A solid aggregate of one or more minerals (or mineraloids) without a fixed overall chemical formula; granite, for example, is made of quartz, feldspar, and mica.

Key differences at a glance

  • Composition
    • Minerals have a specific chemical formula and are the same substance all the way through.
* Rocks are made of multiple minerals (or sometimes just one, like quartzite) mixed together, so their overall composition can vary.
  • Structure
    • Minerals have an ordered internal crystal structure that gives them characteristic shapes and properties.
* Rocks are collections of mineral grains; the rock itself does not have one single crystal structure throughout.
  • Examples
    • Minerals: quartz, calcite, mica, gypsum.
* Rocks: granite, basalt, sandstone, limestone, marble.

How they form

  • Minerals
    • Crystallize from cooling magma or lava.
    • Precipitate from water (like salt crystals forming when seawater evaporates).
    • Grow or change during heat and pressure in Earth’s crust (metamorphic processes).
  • Rocks
    • Igneous rocks form when magma or lava cools and solidifies.
    • Sedimentary rocks form when sediments are compacted and cemented.
    • Metamorphic rocks form when existing rocks are transformed by heat and pressure.

Quick mental picture

  • A mineral is like a single ingredient (e.g., sugar).
  • A rock is like a baked cookie made from several ingredients (different minerals) mixed together.

Short forum-style takeaway

Minerals are the building blocks ; rocks are the things built from them. A rock can be made of many minerals, but a mineral is one specific substance with a set formula and crystal structure.

Information gathered from public forums or data available on the internet and portrayed here.