Demartinite is an extremely rare potassium fluorosilicate mineral found primarily as a fumarolic sublimation product at Mount Vesuvius. It typically forms small, colorless, tabular crystals or delicate crusts in volcanic vents where fluorine-rich gases have interacted with the local environment.
Is this demartinite?
3-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 demartinite with a known reference. Demartinite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Match the color rangeCompare against the expected color range: colorless.
- 3Look at form & habitCrystal system: hexagonal. Typical habit: hexagonal.
Often confused with
Demartinite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside demartinite
Minerals reported to co-occur with demartinite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₂SiF₆
- Mohs hardness
- 2
- Density
- 2.85 g/cm³
- Colors
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Hexagonal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Near volcanic fumaroles
Where rockhounds find demartinite
Classic worldwide localities
- Fгош La Fossa Crater, Vulcano, Aeolian Islands, Italy
Field-hunting tip
Where it forms: Near volcanic fumaroles. If you start seeing hieratite, avogadrite, knasibfite in float, you are in the right ground. Typical habit: hexagonal. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify demartinite?+
Where is demartinite found?+
Is demartinite safe to handle?+
What rocks look like demartinite?+
What minerals are found with demartinite?+
What kind of rock does demartinite form in?+
What is demartinite used for?+
Find demartinite on the map
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