Tubulite is a descriptive term for cylindrical or tubular fossil casts, often formed by the infilling of burrows or plant stems within carbonate sediment. These structures are frequently composed of calcite or dolomite and are commonly found weathered out of limestone or dolomite strata in the American Midwest.

Hardness

3-4

Mohs

Luster

Dull to Earthy

Streak

White

Transparency

Opaque

fossilcommon

Tubulite

Hardness: 3-4
Luster: Dull to Earthy
Streak: White
Transparency: Opaque

Is this tubulite?

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 tubulite with a known reference. Tubulite sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Tubulite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Tubulite typically shows a dull to earthy luster.
4
Match the color range
Compare against the expected color range: gray, brown, white, tan.
5
Look at form & habit
Typical habit: tubular.

Often confused with

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

mineral

Calcite

Mohs 3

How to tell apart: Luster reads dull to earthy on Tubulite and vitreous on Calcite.

How to tell apart: Luster reads dull to earthy on Tubulite and vitreous on Dolomite.

Compare →

Often found alongside tubulite

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

All properties

Mohs hardness: 3-4
Density: 2.6-2.7 g/cm³
Colors: Gray Brown White Tan
Streak: White
Luster: Dull to Earthy
Transparency: Opaque
Crystal habit: Tubular
Cleavage: None
Rarity: Common
Uses: Collector, Decorative
Host rock: Sedimentary Limestone or Dolomite
Typical price: $5-50 depending on specimen quality and size

Where rockhounds find tubulite

Classic worldwide localities

Illinois, USA
Iowa, USA
Wisconsin, USA

Field-hunting tip

Look in sedimentary limestone or dolomite country — that is the host setting where tubulite typically forms. If you start seeing calcite, dolomite, quartz in float, you are in the right ground. Field specimens usually show a tubular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tubulite?+

Mohs hardness is 3-4. It typically shows a dull to earthy luster. The streak is white. Common colors include gray, brown, white, tan.

Where is tubulite found?+

Notable localities include Illinois, USA; Iowa, USA; Wisconsin, USA.

How much is tubulite worth?+

Typical asking prices fall in the range of $5-50 depending on specimen quality and size. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like tubulite?+

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

What minerals are found with tubulite?+

Tubulite commonly co-occurs with calcite, dolomite, quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tubulite form in?+

Tubulite typically forms in sedimentary limestone or dolomite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tubulite used for?+

Tubulite is used in collector, decorative.

Find tubulite on the map

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