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, so Ferroericssonite leaves brownish, Bafertisite leaves yellowish; luster reads submetallic on Ferroericssonite and pearly on Bafertisite.
How to tell apart: Streak differs, so 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, 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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