Dolostone is a sedimentary rock composed primarily of the mineral dolomite, often formed through the chemical alteration of limestone. It typically exhibits a grainy, massive texture and can be distinguished from limestone by its slower, weaker reaction to dilute hydrochloric acid, especially when unpowdered.

Hardness

3.5-4

Mohs

Luster

Dull

Transparency

Opaque

sedimentarycommon

Dolostone

Also: Dolomite Rock, Magnesian Limestone

Hardness: 3.5-4
Luster: Dull
Transparency: Opaque

Is this dolostone?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch dolostone with a known reference. Dolostone sits at Mohs 3.5-4, softer than the next harder reference, harder than the previous one.
2
Read the texture
Look at a fresh break with a hand lens. Texture: Bedded or unbedded.
3
Pick out the minerals
Composition: High percentage of the mineral dolomite, mostly formed by magnesium replacement of limestone. Identify the two or three most abundant grains.
4
Read the luster
Hold the specimen under a strong light. Luster: dull.
5
Match the color range
Compare against the expected color range: gray, white, buff, brown, tan, pink.

Often confused with

Dolostone vs. its common look-alikes, and how to tell them apart in the field.

How to tell apart: Luster reads dull on Dolostone and subvitreous on Marble.

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Often found alongside dolostone

Minerals reported to co-occur with dolostone. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Mohs hardness: 3.5-4
Density: 2.8-2.9 g/cm³
Colors: Gray WhiteBuffBrown Tan Pink
Luster: Dull
Transparency: Opaque
Rarity: Common
Uses: Construction, Industrial, Decorative, Collector
Host rock: sedimentary basins
Texture: Bedded or unbedded
Composition: High percentage of the mineral dolomite, mostly formed by magnesium replacement of limestone

Where rockhounds find dolostone

Classic worldwide localities

Dolomites (Italy)
Niagara Escarpment (North America)
United Kingdom
China

Field-hunting tip

Where it forms: sedimentary basins. If you start seeing calcite, dolomite, quartz in float, you are in the right ground.

Common questions

How do you identify dolostone?+

Mohs hardness is 3.5-4. Texture: Bedded or unbedded. Composition: High percentage of the mineral dolomite, mostly formed by magnesium replacement of limestone. Luster: dull. Common colors include gray, white, buff, brown.

Where is dolostone found?+

Notable localities include Dolomites (Italy); Niagara Escarpment (North America); United Kingdom; China.

What rocks look like dolostone?+

Dolostone is most often confused with Limestone, Marble. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with dolostone?+

Dolostone commonly co-occurs with Calcite, Dolomite, Quartz, Gypsum. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does dolostone form in?+

Where it forms: sedimentary basins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is dolostone used for?+

Dolostone is used in construction, industrial, decorative, collector.

Find dolostone on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.