Bellbergite is an exceptionally rare member of the osumilite group found as tiny prismatic crystals in volcanic rocks. It is primarily known for its type locality at the Bellberg volcano in the Eifel region of Germany. Collectors typically seek it out as a micro-mineral within the vugs of alkaline volcanic ejecta.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareOsumilite Group family

Bellbergite

Hardness: ~5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this bellbergite?

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 bellbergite with a known reference. Bellbergite 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: vitreous.
4
Match the color range
Compare against the expected color range: colorless, white.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: pyramidal.

Often confused with

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

mineral

Osumilite

Mohs 5-5.5

How to tell apart: Streak differs, so Bellbergite leaves white, Osumilite leaves blue-gray.

Often found alongside bellbergite

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

All properties

Chemical formula: (K,Ba,Sr)₂Sr₂Ca₂(Ca,Na)₄(Si,Al)₃₆O₇₂·30H₂O
Mohs hardness: ~5
Density: 2.20 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Hexagonal
Crystal habit: Pyramidal
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In leucite tephrite lava at contacts between lava and calcium-rich xenoliths

Where rockhounds find bellbergite

Classic worldwide localities

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

Field-hunting tip

Where it forms: In leucite tephrite lava at contacts between lava and calcium-rich xenoliths. If you start seeing sanidine, clinopyroxene, pyrrhotite in float, you are in the right ground. Typical habit: pyramidal. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify bellbergite?+

Mohs hardness is ~5. Luster: vitreous. The streak is white. Common colors include colorless, white.

Where is bellbergite found?+

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

What rocks look like bellbergite?+

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

What minerals are found with bellbergite?+

Bellbergite commonly co-occurs with Sanidine, Clinopyroxene, Pyrrhotite, Thompsonite, Ettringite, Willhendersonite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does bellbergite form in?+

Where it forms: In leucite tephrite lava at contacts between lava and calcium-rich xenoliths. Working float back to the host body is the standard way to chase a fresh occurrence.

What is bellbergite used for?+

Bellbergite is used in collector.

Find bellbergite on the map

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