Wurtzilite is a rare, rubbery, hydrocarbon-based organic mineraloid primarily found in the Uinta Basin of Utah. It occurs as massive, dark, elastic or brittle veins within oil-bearing shales and is valued by collectors of unusual organic minerals.

Hardness

3-4

Mohs

Luster

Resinous

Streak

Brown

Transparency

Opaque

mineralrare

Wurtzilite

Also: Elaterite

Hardness: 3-4
Luster: Resinous
Streak: Brown
Transparency: Opaque

No image

Is this wurtzilite?

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 wurtzilite with a known reference. Wurtzilite 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. Streak: brown.
3
Read the luster
Hold the specimen under a strong light. Luster: resinous.
4
Match the color range
Compare against the expected color range: black, brown.
5
Look at form & habit
Crystal system: amorphous. Typical habit: massive.

Often confused with

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

mineral

Gilsonite

Mohs 2-2.5

How to tell apart: Luster reads resinous on Wurtzilite and bright on Gilsonite.

All properties

Mohs hardness: 3-4
Density: 1.05 g/cm³
Colors: Black Brown
Streak: Brown
Luster: Resinous
Transparency: Opaque
Crystal system: Amorphous
Crystal habit: Massive
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: sedimentary veins in oil shale

Where rockhounds find wurtzilite

3 mapped spots

Classic worldwide localities

Uinta Basin, Utah USA

Field-hunting tip

Where it forms: sedimentary veins in oil shale. If you start seeing bitumen, oil shale in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah. Start trip planning there.

Browse 3 U.S. spots for wurtzilite →

Common questions

How do you identify wurtzilite?+

Mohs hardness is 3-4. Luster: resinous. The streak is brown. Common colors include black, brown.

Where is wurtzilite found?+

Notable localities include Uinta Basin, Utah USA.

Can I find wurtzilite in the United States?+

RockHoundR maps 3 wurtzilite rockhounding spots across 1 U.S. states. The top states are Utah.

What rocks look like wurtzilite?+

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

What minerals are found with wurtzilite?+

Wurtzilite commonly co-occurs with Bitumen, Oil shale. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does wurtzilite form in?+

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

What is wurtzilite used for?+

Wurtzilite is used in collector.

Find wurtzilite on the map

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