The Dunham Dolomite is a significant Lower Cambrian sedimentary formation primarily found in the Lake Champlain region of Vermont. It is a buff-to-grey weathering rock characterized by its dolomitic composition and is often studied for its stratigraphy and fossil content within the Appalachian thrust belt.

Hardness

3.5-4

Mohs

Luster

Dull

Transparency

Opaque

sedimentarycommonSedimentary Rock family

Dunham Dolomite

Hardness: 3.5-4
Luster: Dull
Transparency: Opaque

Is this dunham dolomite?

4-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 dunham dolomite with a known reference. Dunham Dolomite sits at Mohs 3.5-4, softer than the next harder reference, harder than the previous one.
2
Pick out the minerals
Composition: Dolomite (Cambrian). Identify the two or three most abundant grains.
3
Read the luster
Hold the specimen under a strong light. Luster: dull.
4
Match the color range
Compare against the expected color range: gray, buff, tan, brown.

Often confused with

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

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

Compare →

Often found alongside dunham dolomite

Minerals reported to co-occur with dunham dolomite. 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: GrayBuffTan Brown
Luster: Dull
Transparency: Opaque
Rarity: Common
Uses: Construction, Architectural stone, Educational
Host rock: Sedimentary basins
Composition: Dolomite (Cambrian)

Where rockhounds find dunham dolomite

1 mapped spots

Classic worldwide localities

Vermont
New England
Appalachian region

Field-hunting tip

Where it forms: Sedimentary basins. If you start seeing calcite, quartz, clay minerals in float, you are in the right ground. In the U.S., the densest reported localities are in Vermont. Start trip planning there.

Browse 1 U.S. spots for dunham dolomite →

Common questions

How do you identify dunham dolomite?+

Mohs hardness is 3.5-4. Composition: Dolomite (Cambrian). Luster: dull. Common colors include gray, buff, tan, brown.

Where is dunham dolomite found?+

Notable localities include Vermont; New England; Appalachian region.

Can I find dunham dolomite in the United States?+

RockHoundR maps 1 dunham dolomite rockhounding spots across 1 U.S. states. The top states are Vermont.

What rocks look like dunham dolomite?+

Dunham Dolomite 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 dunham dolomite?+

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

What kind of rock does dunham dolomite 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 dunham dolomite used for?+

Dunham Dolomite is used in construction, architectural stone, educational.

Find dunham dolomite on the map

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