Fredrikssonite is a rare manganese-magnesium borate mineral that typically forms as small, prismatic crystals within metamorphosed ore bodies. It is famously associated with the Långban deposit in Sweden, often appearing as distinct, colored crystals embedded in a matrix of other manganese minerals. Collectors prize it for its unique chemistry and extreme rarity in fine crystal form.
Is this fredrikssonite?
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 fredrikssonite with a known reference. Fredrikssonite 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: pale brown to yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to dull.
- 4Match the color rangeCompare against the expected color range: reddish brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic.
Often confused with
Fredrikssonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Fredrikssonite leaves pale brown to yellow, Ludwigite leaves black to greenish black; luster reads vitreous to dull on Fredrikssonite and submetallic on Ludwigite.
How to tell apart: Fredrikssonite is noticeably harder (Mohs ~6 vs. 5); streak differs, so Fredrikssonite leaves pale brown to yellow, Vonsenite leaves brownish black; luster reads vitreous to dull on Fredrikssonite and metallic to submetallic, silky if fibrous on Vonsenite.
Often found alongside fredrikssonite
Minerals reported to co-occur with fredrikssonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mg₂MnO₂(BO₃)
- Mohs hardness
- ~6
- Density
- 3.84 g/cm³
- Colors
- Streak
- Pale brown to yellow
- Luster
- Vitreous to dull
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic
- Cleavage
- One, poor, and a second, very poor
- Rarity
- Rare
- Uses
- Collector
- Host rock
- From a metamorphosed Fe–Mn orebody
Where rockhounds find fredrikssonite
Classic worldwide localities
- Långban, Värmland, Sweden
Field-hunting tip
Where it forms: From a metamorphosed Fe–Mn orebody. If you start seeing hausmannite, manganoan calcite, brucite in float, you are in the right ground. Typical habit: prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify fredrikssonite?+
Where is fredrikssonite found?+
What rocks look like fredrikssonite?+
What minerals are found with fredrikssonite?+
What kind of rock does fredrikssonite form in?+
What is fredrikssonite used for?+
Find fredrikssonite on the map
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