Jasmundite is a rare calcium-iron silicate mineral discovered in the combustion metamorphic rocks of the Jasmund cliff on Rügen Island. It typically occurs as minute anhedral grains within rocks formed by the burning of bituminous marls, making it a highly localized curiosity for advanced mineral collectors.

Hardness

Mohs

Luster

Resinous

Streak

White

Transparency

Semitransparent

mineralrare

Jasmundite

Hardness: ~5
Luster: Resinous
Streak: White
Transparency: Semitransparent

Is this jasmundite?

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 jasmundite with a known reference. Jasmundite sits at Mohs ~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: resinous.
4
Match the color range
Compare against the expected color range: brownish green, greenish brown, dark brown.
5
Look at form & habit
Crystal system: tetragonal. Typical habit: anhedral grains.

Often confused with

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

How to tell apart: Larnite is the harder of the two (Mohs 6 vs. ~5); luster reads resinous on Jasmundite and vitreous on Larnite.

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Often found alongside jasmundite

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

All properties

Chemical formula: Ca₁₁O₂(SiO₄)₄S
Mohs hardness: ~5
Density: 3.03 g/cm³
Colors: Brownish green Greenish brown Dark brown
Streak: White
Luster: Resinous
Transparency: Semitransparent
Crystal system: Tetragonal
Crystal habit: Anhedral grains
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In metamorphosed limestone inclusions in basalt

Where rockhounds find jasmundite

Classic worldwide localities

Bellerberg volcano, two km north of Mayen, Eifel district, Germany

Field-hunting tip

Where it forms: In metamorphosed limestone inclusions in basalt. If you start seeing mayenite, brownmillerite, larnite in float, you are in the right ground. Typical habit: anhedral grains. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify jasmundite?+

Mohs hardness is ~5. Luster: resinous. The streak is white. Common colors include brownish green, greenish brown, dark brown.

Where is jasmundite found?+

Notable localities include Bellerberg volcano, two km north of Mayen, Eifel district, Germany.

What rocks look like jasmundite?+

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

What minerals are found with jasmundite?+

Jasmundite commonly co-occurs with Mayenite, Brownmillerite, Larnite, Portlandite, Ettringite, Calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does jasmundite form in?+

Where it forms: In metamorphosed limestone inclusions in basalt. Working float back to the host body is the standard way to chase a fresh occurrence.

What is jasmundite used for?+

Jasmundite is used in collector.

Find jasmundite on the map

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