Ferriallanite-(Ce) is a rare member of the epidote group characterized by high iron content and significant cerium substitution. Collectors typically find it as dark, opaque, prismatic crystals or massive aggregates in alkaline igneous environments. Due to its radioactive nature, it is prized by advanced collectors and should be stored with appropriate precautions.
Is this ferriallanite-(ce)?
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 ferriallanite-(ce) with a known reference. Ferriallanite-(Ce) sits at Mohs 6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: aggregates, subhedral crystals.
Often confused with
Ferriallanite-(Ce) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ferriallanite-(Ce) leaves brown, Allanite leaves gray; luster reads resinous on Ferriallanite-(Ce) and submetallic on Allanite.
How to tell apart: Streak differs, so Ferriallanite-(Ce) leaves brown, Epidote leaves grayish white; luster reads resinous on Ferriallanite-(Ce) and vitreous, pearly, somewhat resinous on Epidote.
Often found alongside ferriallanite-(ce)
Minerals reported to co-occur with ferriallanite-(ce). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- {CaCe}{Fe³⁺Fe²⁺}AlFe³⁺(Si₂O₇)(SiO₄)O(OH)
- Mohs hardness
- 6
- Density
- 4.22 g/cm³
- Colors
- Streak
- Brown
- Luster
- Resinous
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Aggregates, subhedral crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Of metasomatic origin in alkaline granitic pegmatite
Where rockhounds find ferriallanite-(ce)
Classic worldwide localities
- Mount Ylyn Khuren, Altia Range, Mongolian People's Republic (type locality)
Field-hunting tip
Where it forms: Of metasomatic origin in alkaline granitic pegmatite. If you start seeing aegirine, β-fergusonite-, hingganite- in float, you are in the right ground. Typical habit: aggregates, subhedral crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferriallanite-(ce)?+
Where is ferriallanite-(ce) found?+
Is ferriallanite-(ce) safe to handle?+
What rocks look like ferriallanite-(ce)?+
What minerals are found with ferriallanite-(ce)?+
What kind of rock does ferriallanite-(ce) form in?+
What is ferriallanite-(ce) used for?+
Find ferriallanite-(ce) on the map
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