Kladnoite is an extremely rare organic mineral found as sublimation crusts in burning coal mine waste piles. It is highly unstable and water-soluble, requiring careful preservation away from humidity. Collectors prize it for its unique chemical origin as a naturally occurring organic phthalimide derivative.

Hardness

1.5

Mohs

Luster

Dull

Streak

White

Transparency

Semitransparent

mineralrare

Kladnoite

Hardness: 1.5
Luster: Dull
Streak: White
Transparency: Semitransparent

Is this kladnoite?

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 kladnoite with a known reference. Kladnoite sits at Mohs 1.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: dull.
4
Match the color range
Compare against the expected color range: white, colorless.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: sublimation crusts, fine crystalline aggregates.

Often found alongside kladnoite

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

All properties

Chemical formula: C₆H₄(CO)₂NH
Mohs hardness: 1.5
Density: 1.47 g/cm³
Colors: White Colorless
Streak: White
Luster: Dull
Transparency: Semitransparent
Crystal system: Monoclinic
Crystal habit: Sublimation crusts, fine crystalline aggregates
Cleavage: Good
Rarity: Rare
Uses: Collector
Host rock: Formed as a result of fires in coal heaps

Where rockhounds find kladnoite

Classic worldwide localities

Scholler coal mine, Libušín, Kladno coal basin, about 30 km west-northwest of Prague, and at Radvanice, Czech Republic

Field-hunting tip

Where it forms: Formed as a result of fires in coal heaps. If you start seeing sal-ammoniac, sulfur, boussingaultite in float, you are in the right ground. Typical habit: sublimation crusts, fine crystalline aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify kladnoite?+

Mohs hardness is 1.5. Luster: dull. The streak is white. Common colors include white, colorless.

Where is kladnoite found?+

Notable localities include Scholler coal mine, Libušín, Kladno coal basin, about 30 km west-northwest of Prague, and at Radvanice, Czech Republic.

What minerals are found with kladnoite?+

Kladnoite commonly co-occurs with Sal-ammoniac, Sulfur, Boussingaultite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does kladnoite form in?+

Where it forms: Formed as a result of fires in coal heaps. Working float back to the host body is the standard way to chase a fresh occurrence.

What is kladnoite used for?+

Kladnoite is used in collector.

Find kladnoite on the map

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