Ferroceladonite is a phyllosilicate mineral occurring primarily as earthy or micaceous coatings within the vesicles of volcanic rocks. It is visually distinguished from standard celadonite by its iron-dominant composition and is most frequently collected as an attractive green filling in basalt cavities.
Is this ferroceladonite?
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 ferroceladonite with a known reference. Ferroceladonite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: paler green.
- 3Read the lusterHold the specimen under a strong light. Luster: earthy.
- 4Match the color rangeCompare against the expected color range: dark bluish green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: microscopic crystals.
Often confused with
Ferroceladonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ferroceladonite leaves paler green, Celadonite leaves greenish white; luster reads earthy on Ferroceladonite and dull on Celadonite.
How to tell apart: Streak differs, so Ferroceladonite leaves paler green, Glauconite leaves light green; luster reads earthy on Ferroceladonite and dull, glistening on Glauconite.
How to tell apart: Streak differs, so Ferroceladonite leaves paler green, Chlorite leaves white; luster reads earthy on Ferroceladonite and pearly on Chlorite.
Often found alongside ferroceladonite
Minerals reported to co-occur with ferroceladonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KFeFeSi₄O₁₀(OH)₂
- Mohs hardness
- 2-2.5
- Density
- 3.05 g/cm³
- Colors
- Dark bluish green
- Streak
- Paler green
- Luster
- Earthy
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Microscopic crystals
- Cleavage
- Perfect on {001}
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- In an altered crystal-vitric tuff associated with ferroaluminoceladonite
Where rockhounds find ferroceladonite
Classic worldwide localities
- Hokonui Hills, Southland, New Zealand (type locality)
Field-hunting tip
Where it forms: In an altered crystal-vitric tuff associated with ferroaluminoceladonite. If you start seeing heulandite, stilbite, calcite in float, you are in the right ground. Typical habit: microscopic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferroceladonite?+
Where is ferroceladonite found?+
What rocks look like ferroceladonite?+
What minerals are found with ferroceladonite?+
What kind of rock does ferroceladonite form in?+
What is ferroceladonite used for?+
Find ferroceladonite on the map
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