Quartz vs Calcite: How to Tell the Difference

Quartz and calcite can look surprisingly similar, especially when both occur as pale, translucent or colorless crystals. A few simple observations can usually separate them without guessing.

Hardness is the fastest clue

Quartz has a Mohs hardness of 7, while calcite is about 3. Quartz can scratch ordinary glass; calcite generally cannot. When testing a collector specimen, use caution and avoid damaging an important crystal face.

Look at cleavage

Calcite has strong rhombohedral cleavage, so broken surfaces often form repeated slanted planes. Quartz does not have true cleavage and is more likely to show irregular or conchoidal fracture.

Compare crystal habit

Quartz commonly forms six-sided prismatic crystals with pointed terminations. Calcite can form rhombohedra, scalenohedra and many other habits, sometimes creating blocky, dogtooth or bladed-looking crystals.

Context matters

Mineral associations and locality can help. Calcite commonly occurs with fluorite and metallic ores, while quartz is widespread in hydrothermal veins, pegmatites and many other environments.

Compare real examples in our quartz specimens and calcite specimens collections.