Dolomite is a common carbonate mineral that forms distinct, often saddle-shaped rhombohedral crystals. It is easily distinguished from calcite because it will only effervesce in dilute hydrochloric acid when powdered.
Is this dolomite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch dolomite with a known reference. Dolomite sits at Mohs 3.5-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to pearly.
- 4Match the color rangeCompare against the expected color range: white, gray, pink, colorless, brown, yellow, reddish white, brownish white.
- 5Look at form & habitCrystal system: trigonal. Typical habit: blocky, crystalline, massive.
Often confused with
Dolomite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside dolomite
Minerals reported to co-occur with dolomite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaMg(CO₃)₂
- Mohs hardness
- 3.5-4
- Density
- 2.86 g/cm³
- Streak
- White
- Luster
- Vitreous to pearly
- Transparency
- Transparent to translucent
- Crystal system
- Trigonal
- Crystal habit
- Blocky, crystalline, massive
- Cleavage
- On {1011}, perfect; on {0221}, a parting
- Rarity
- Common
- Uses
- Industrial, Collector, Construction
- Host rock
- Formed by diagenesis or hydrothermal metasomatism of limestone; a primary phase in hypersaline sedimentary environments; a major component of some contact metamorphic rocks and marbles; a gangue in hydrothermal veins
Where rockhounds find dolomite
58 mapped spotsClassic worldwide localities
- Lockport, Niagara Co., eastward to Walworth, Wayne Co., New York, USA
- Stony Point, Alexander Co., North Carolina, USA
- Mississippi Valley region, in the Tri-State district, at Joplin, Jasper Co., Missouri, USA
- Galena, Cherokee Co., Kansas, USA
- Traversella and Brosso, Piedmont, Italy
- Eugui, Navarra Province, Spain
U.S. states with dolomite
Each link opens a state-specific list of mapped rockhounding spots that produce dolomite.
Field-hunting tip
Where it forms: Formed by diagenesis or hydrothermal metasomatism of limestone; a primary phase in hypersaline sedimentary environments; a major component of some contact metamorphic rocks and marbles; a gangue in hydrothermal veins. If you start seeing fluorite, barite, calcite in float, you are in the right ground. Typical habit: blocky, crystalline, massive. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Missouri, Tennessee, West Virginia. Start trip planning there.
More dolomite photos
Common questions
How do you identify dolomite?+
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Can I find dolomite in the United States?+
What rocks look like dolomite?+
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Find dolomite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
