Hannebachite is a rare calcium sulfite hydrate typically found in volcanic environments as a secondary mineral. It occurs as delicate, transparent to white platy crystals, most famously discovered in the volcanic rocks of the Eifel region in Germany. It is highly sought after by mineral collectors due to its restricted occurrences and fragile nature.
Is this hannebachite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch hannebachite with a known reference. Hannebachite sits at Mohs ~3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: platy or tabular crystals, often in radiating aggregates.
Often confused with
Hannebachite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Hannebachite is noticeably harder (Mohs ~3.5 vs. 1.5-2); luster reads vitreous on Hannebachite and subvitreous, pearly on {010} cleavages, silky if fibrous on Gypsum.
How to tell apart: Luster reads vitreous on Hannebachite and earthy on Bassanite.
Often found alongside hannebachite
Minerals reported to co-occur with hannebachite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaSO₃·0.5H₂O
- Mohs hardness
- ~3.5
- Density
- 2.52 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Platy or tabular crystals, often in radiating aggregates
- Cleavage
- Perfect on {110}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Lining cavities in blocks of melilite-nepheline-leucitite at the base of a volcano
Where rockhounds find hannebachite
Classic worldwide localities
- Hannebacher Ley volcano, one km east-northeast of Hannebach, and at Kalem, near Birresborn, Eifel district, Germany
Field-hunting tip
Where it forms: Lining cavities in blocks of melilite-nepheline-leucitite at the base of a volcano. If you start seeing calcite, aragonite, gypsum in float, you are in the right ground. Typical habit: platy or tabular crystals, often in radiating aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
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Find hannebachite on the map
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