Rondorfite is a very rare silicate mineral found in xenoliths within volcanic ejecta. It typically occurs as small, colorless dodecahedral crystals and is known primarily from the Bellerberg Volcano in the Eifel region of Germany.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareGarnet Group family

Rondorfite

Hardness: 6
Luster: Vitreous
Streak: White
Transparency: Transparent

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Is this rondorfite?

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 rondorfite with a known reference. Rondorfite sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Rondorfite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Rondorfite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, white.
5
Look at form & habit
Crystal system: cubic. Typical habit: dodecahedral crystals.

Often confused with

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

Often found alongside rondorfite

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

All properties

Chemical formula: Ca₈Mg(SiO₄)₄Cl₂
Mohs hardness: 6
Density: 3.1 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Cubic
Crystal habit: Dodecahedral Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Xenoliths in Volcanic Rocks
Typical price: $50-500 depending on specimen size and clarity

Where rockhounds find rondorfite

Classic worldwide localities

Bellerberg Volcano, Eifel, Germany

Field-hunting tip

Look in xenoliths in volcanic rocks country — that is the host setting where rondorfite typically forms. If you start seeing ettringite, afwillite, hillebrandite in float, you are in the right ground. Field specimens usually show a dodecahedral crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify rondorfite?+

Mohs hardness is 6. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white.

Where is rondorfite found?+

Notable localities include Bellerberg Volcano, Eifel, Germany.

How much is rondorfite worth?+

Typical asking prices fall in the range of $50-500 depending on specimen size and clarity. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like rondorfite?+

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

What minerals are found with rondorfite?+

Rondorfite commonly co-occurs with Ettringite, Afwillite, Hillebrandite, Mayenite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does rondorfite form in?+

Rondorfite typically forms in xenoliths in volcanic rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is rondorfite used for?+

Rondorfite is used in collector.

Find rondorfite on the map

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