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

Streak

White

Transparency

Opaque

sedimentarycommonSedimentary Rock family

Dunham Dolomite

Hardness: 3.5-4
Luster: Dull
Streak: White
Transparency: Opaque

Is this dunham dolomite?

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 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
Check the streak
Drag the specimen across an unglazed porcelain plate. Dunham Dolomite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Dunham Dolomite typically shows a dull luster.
4
Match the color range
Compare against the expected color range: gray, buff, tan, brown.
5
Look at form & habit
Typical habit: massive.

Often confused with

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

sedimentary

Limestone

Mohs 3

How to tell apart: Luster reads dull on Dunham Dolomite and dull to earthy on Limestone.

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: Gray Buff Tan Brown
Streak: White
Luster: Dull
Transparency: Opaque
Crystal habit: Massive
Cleavage: None
Rarity: Common
Uses: Construction, Architectural Stone, Educational
Host rock: Sedimentary Basins
Typical price: $1-10 per specimen

Where rockhounds find dunham dolomite

1 mapped spots

Classic worldwide localities

Vermont
New England
Appalachian region

Field-hunting tip

Look in sedimentary basins country — that is the host setting where dunham dolomite typically forms. If you start seeing calcite, quartz, clay minerals in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop. 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. It typically shows a dull luster. The streak is white. 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.

How much is dunham dolomite worth?+

Typical asking prices fall in the range of $1-10 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

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?+

Dunham Dolomite typically forms in 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.