LithoMap

Mineral identification comparison

Calcite vs. dolomite: how to tell them apart

Calcite and dolomite are rhombohedral carbonate minerals that commonly look alike. Calcite is softer and fizzes readily with cold dilute acid; dolomite is slightly harder and usually reacts weakly unless powdered.

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Calcite mineral specimen with pale translucent crystals
CalciteCarbonate mineral · CaCO₃Photo: Raimond Spekking · CC BY-SA 4.0
Pale dolomite crystals from Azcárate Quarry in Eugui, Navarre, Spain
DolomiteCarbonate mineral · CaMg(CO₃)₂Photo: Didier Descouens · CC BY-SA 4.0
Quick answer

The most useful distinction

Use a controlled acid test on expendable material. A clean calcite surface effervesces immediately; dolomite usually needs powdering to produce an obvious cold-acid reaction.

Side-by-side evidence

Calcite and Dolomite comparison table

PropertyCalciteDolomiteHow to use it
HardnessMohs 3; scratched by copperMohs 3.5 to 4; resists copper more stronglyHardness supports the acid response when surfaces are fresh.
Acid responseVigorous effervescence on a clean unpowdered surfaceWeak or delayed on a clean surface; stronger when powderedThis is the standard practical separation under controlled conditions.
CleavageThree perfect directions forming rhombohedraThree perfect directions forming rhombohedraCleavage confirms carbonate form but does not separate the pair.
Typical crystal appearanceMany habits including rhombohedra, scalenohedra, and transparent formsRhombohedra, sometimes with curved saddle-shaped faces; commonly pearlyHabit helps only when well-developed crystals are present.
Field sequence

A practical identification sequence

  1. 1

    Inspect a fresh uncoated surface and confirm rhombohedral cleavage if visible.

  2. 2

    Compare resistance to a copper point on an inconspicuous edge.

  3. 3

    Apply one drop of dilute acid to an expendable clean surface.

  4. 4

    If reaction is weak, powder a tiny chip and retest before favoring dolomite.

Limits and cautions

Where the distinction gets difficult

  • Calcite and dolomite commonly occur together and can produce mixed reactions.
  • Temperature, acid strength, coatings, grain size, and weathering affect effervescence.
  • Do not acid-test cave formations, fossils, monuments, finished stone, or valuable specimens.

Use several independent observations. This comparison supports preliminary field identification, not laboratory confirmation, appraisal, proof of origin, or collecting permission.

Common questions

Calcite vs. dolomite FAQ

Does dolomite fizz in acid?

Dolomite commonly reacts weakly on a cold intact surface and much more clearly when powdered. Warm or stronger acid also increases reaction.

Can color separate calcite and dolomite?

No. Both can be white, gray, tan, pink, colorless, or stained by impurities.

Is dolomite a mineral or a rock?

Dolomite is a mineral. Dolostone is the preferred name for a sedimentary rock composed mostly of the mineral dolomite.

Source basis

Authoritative sources

LithoMap wrote this comparison in original language from the physical properties and geological concepts supported by these public scientific references.

Editorial review: September 17, 2026.

Resolve another lookalike

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