Geology basics
Rock vs Mineral vs Crystal
A mineral is a naturally occurring solid with a defined chemical composition and ordered atomic structure. A rock is a mixture of one or more minerals (or mineraloids) that formed together as a geological unit. A crystal describes the geometric, ordered form a mineral can take when it grows freely — so every crystal specimen is a mineral (or mineral aggregate), but not every rock is a single mineral, and not every mineral specimen shows obvious crystal faces.
What is a mineral?
Minerals have diagnostic properties collectors can check: Mohs hardness, streak, luster, cleavage, and crystal system. Quartz (SiO₂, Mohs 7), pyrite, and hematite are minerals — each has a defined chemistry and structure. Use the minerals hub or the mineral identifier page for property-first ID.
What is a rock?
Rocks are geological mixtures. Granite is a rock made of quartz + feldspar + mica; sandstone is cemented sand grains; basalt is fine igneous rock. A geode is a rock cavity that may host mineral crystals inside. Start with the rocks hub or how to identify rock types for igneous vs sedimentary vs metamorphic triage.
What is a crystal?
In collector language, “crystal” usually means a mineral specimen showing crystal faces or a clear crystalline habit — amethyst, citrine, clear quartz. Chemically these are still minerals (often quartz varieties). RockScan’s crystals hub and crystal identifier focus on geological specimens, not glassware.
Quick comparison
- Mineral = defined solid (chemistry + structure) — check Mohs, streak, luster.
- Rock = mixture / geological unit — check texture, grains, banding, fossils.
- Crystal = ordered growth form of a mineral — check habit and faces; still verify hardness.
How RockScan maps the three
Photo ID returns a ranked suggestion, then you confirm on the right hub: outdoor textures on rocks, property checks on minerals, habit and color varieties on crystals. Unsure what you found? Ask what rock is this, or open the online studio / rock identifier app.
Browse top specimens by class
Also: gem identifier · directory · rock types guide.