Baculites are extinct cephalopods characterized by their straight, rather than coiled, chambered shells. Collectors typically find them as fossils within marine shales and limestones, often with intricate suture patterns visible on the exterior when the outer shell layer has eroded.

Hardness

3-4

Mohs

Luster

Dull

Transparency

Opaque

fossilcommon

Baculite

Hardness: 3-4
Luster: Dull
Transparency: Opaque

Is this baculite?

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 baculite with a known reference. Baculite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
2
Name the organism
Decide what left the fossil before worrying about the rock. Organism: Straight-shelled ammonite (genus Baculites). Age: Late Cretaceous to the earliest Paleogene (Danian).
3
Read the luster
Hold the specimen under a strong light. Luster: dull.
4
Match the color range
Compare against the expected color range: brown, gray, beige, white.

Often confused with

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

Often found alongside baculite

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

All properties

Mohs hardness: 3-4
Density: 2.6-2.9 g/cm³
Colors: Brown Gray Beige White
Luster: Dull
Transparency: Opaque
Rarity: Common
Uses: Collector, Educational
Host rock: marine sedimentary rock
Organism: Straight-shelled ammonite (genus Baculites)
Age: Late Cretaceous to the earliest Paleogene (Danian)

Where rockhounds find baculite

Classic worldwide localities

South Dakota, USA
Wyoming, USA
Montana, USA
Alberta, Canada
France

Field-hunting tip

Where it forms: marine sedimentary rock. If you start seeing calcite, pyrite, aragonite in float, you are in the right ground.

Common questions

How do you identify baculite?+

Mohs hardness is 3-4. Organism: Straight-shelled ammonite (genus Baculites). Luster: dull. Common colors include brown, gray, beige, white.

Where is baculite found?+

Notable localities include South Dakota, USA; Wyoming, USA; Montana, USA; Alberta, Canada; France.

What rocks look like baculite?+

Baculite is most often confused with Belemnite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with baculite?+

Baculite commonly co-occurs with Calcite, Pyrite, Aragonite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does baculite form in?+

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

What is baculite used for?+

Baculite is used in collector, educational.

Find baculite on the map

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