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. 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: pyramidal.
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
- 2.34 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Pyramidal
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In volcanic scoria
Where rockhounds find montesommaite
Classic worldwide localities
- Pollena, Monte Somma, Campania, Italy
Field-hunting tip
Where it forms: In volcanic scoria. If you start seeing dolomite, calcite, chabazite 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 montesommaite?+
Where is montesommaite found?+
What rocks look like montesommaite?+
What minerals are found with montesommaite?+
What kind of rock does montesommaite form in?+
What is montesommaite used for?+
Find montesommaite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
