Montesommaite is an extremely rare zeolite found almost exclusively in the volcanic rocks of the Monte Somma-Vesuvius complex in Italy. It typically forms as small, colorless, equant crystals within cavities of alkaline volcanic material. Collectors primarily encounter it as micro-specimens associated with other rare volcanic minerals.
Is this montesommaite?
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 montesommaite with a known reference. Montesommaite sits at Mohs 4.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Montesommaite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Montesommaite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: equant crystals.
Often confused with
Montesommaite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside montesommaite
Minerals reported to co-occur with montesommaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₉(Al₉Si₂₃O₆₄)·10H₂O
- Mohs hardness
- 4.5
- Density
- 2.16 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Equant Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Volcanic Ejecta
- Typical price
- $50-300 per specimen
Where rockhounds find montesommaite
Classic worldwide localities
- Monte Somma, Italy
- Vesuvius, Italy
Field-hunting tip
Look in volcanic ejecta country — that is the host setting where montesommaite typically forms. If you start seeing nepheline, leucite, garnet in float, you are in the right ground. Field specimens usually show a equant crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify montesommaite?+
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How much is montesommaite worth?+
What rocks look like montesommaite?+
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Find montesommaite on the map
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