Ferroericssonite is a rare barium-iron silicate found in specific alkaline pegmatitic environments. It typically forms thin, dark, brittle platy crystals that are easily confused with related minerals of the bafertisite group.
Is this ferroericssonite?
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 ferroericssonite with a known reference. Ferroericssonite sits at Mohs 4-5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ferroericssonite leaves a brownish streak.
- 3Read the lusterHold the specimen under a strong light. Ferroericssonite typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: black, dark brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, platy aggregates.
Often confused with
Ferroericssonite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Ferroericssonite is noticeably harder (Mohs 4-5 vs. 3); streak differs — Ferroericssonite leaves brownish, Bafertisite leaves yellowish; luster reads submetallic on Ferroericssonite and pearly on Bafertisite.
How to tell apart: Streak differs — Ferroericssonite leaves brownish, Ericssonite leaves light brown; luster reads submetallic on Ferroericssonite and vitreous on Ericssonite.
Often found alongside ferroericssonite
Minerals reported to co-occur with ferroericssonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- BaFe₂Fe⁺³O(Si₂O₇)(OH)
- Mohs hardness
- 4-5
- Density
- 4.2-4.3 g/cm³
- Colors
- Streak
- Brownish
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Platy Aggregates
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Pegmatites
- Typical price
- $50-300 per specimen
Where rockhounds find ferroericssonite
Classic worldwide localities
- Narsarsuk, Greenland
- Kola Peninsula, Russia
Field-hunting tip
Look in alkaline igneous pegmatites country — that is the host setting where ferroericssonite typically forms. If you start seeing aegirine, microcline, nepheline in float, you are in the right ground. Field specimens usually show a tabular crystals, platy aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ferroericssonite on the map
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