Marchettiite is an extremely rare organic mineral found in volcanic fumaroles. It typically appears as small, yellowish tabular crystals formed by the reaction of volcanic gases with biological matter.
Is this marchettiite?
4-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 marchettiite with a known reference. Marchettiite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 3Match the color rangeCompare against the expected color range: yellow, brownish-yellow.
- 4Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals.
Often confused with
Marchettiite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside marchettiite
Minerals reported to co-occur with marchettiite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- C₅H₇N₅O₃
- Mohs hardness
- 2
- Density
- 1.74 g/cm³
- Colors
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Tabular crystals
- Rarity
- Rare
- Uses
- Collector
- Host rock
- fumarole deposits
Where rockhounds find marchettiite
Classic worldwide localities
- Monte Somma, Italy
Field-hunting tip
Where it forms: fumarole deposits. If you start seeing oxammite, tschermigite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify marchettiite?+
Where is marchettiite found?+
What rocks look like marchettiite?+
What minerals are found with marchettiite?+
What kind of rock does marchettiite form in?+
What is marchettiite used for?+
Find marchettiite on the map
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