Vertumnite is a very rare calcium aluminum silicate hydrate typically found in limestone xenoliths within volcanic complexes. It forms thin, colorless to white, platy crystals that are fragile and often identified through microscopic analysis or professional verification.
Is this vertumnite?
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 vertumnite with a known reference. Vertumnite sits at Mohs 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: monoclinic. Typical habit: prismatic, pseudo hexagonal.
Often confused with
Vertumnite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside vertumnite
Minerals reported to co-occur with vertumnite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₄Al₄Si₄O₆(OH)₂₄·3H₂O
- Mohs hardness
- 5
- Density
- 2.15 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic, pseudo hexagonal
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As late-forming crystals inside a small cavity in phonolite
Where rockhounds find vertumnite
Classic worldwide localities
- Found in a quarry at Campomorto, Montalto di Castro, Lazio, Italy
Field-hunting tip
Where it forms: As late-forming crystals inside a small cavity in phonolite. If you start seeing tobermorite, ettringite in float, you are in the right ground. Typical habit: prismatic, pseudo hexagonal. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify vertumnite?+
Where is vertumnite found?+
What rocks look like vertumnite?+
What minerals are found with vertumnite?+
What kind of rock does vertumnite form in?+
What is vertumnite used for?+
Find vertumnite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
