Janhaugite is a rare silicate mineral belonging to the Wöhlerite group, typically found as small, orange to brown tabular crystals. It is primarily known from the alkaline pegmatites of the Langesundsfjord area in Norway. Collectors generally find it as a microscopic or small-cabinet accessory species associated with other rare alkaline minerals.
Is this janhaugite?
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 janhaugite with a known reference. Janhaugite sits at Mohs 5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: light brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: reddish brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: anhedral grains, prismatic, striated.
Often confused with
Janhaugite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Wöhlerite is the harder of the two (Mohs 6-6.5 vs. 5); streak differs, so Janhaugite leaves light brown, Wöhlerite leaves pale yellow.
How to tell apart: Streak differs, so Janhaugite leaves light brown, Rosenbuschite leaves white.
Often found alongside janhaugite
Minerals reported to co-occur with janhaugite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₃Mn₄Ti₂Si₈O₂₄(O,F,OH)₄
- Mohs hardness
- 5
- Density
- 3.60 g/cm³
- Colors
- Streak
- Light brown
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Anhedral grains, prismatic, striated
- Cleavage
- Distinct on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In both the groundmass and miarolitic cavities in sodium-rich granite
Where rockhounds find janhaugite
Classic worldwide localities
- Gjerdingen, 30 km north of Oslo, Norway
Field-hunting tip
Where it forms: In both the groundmass and miarolitic cavities in sodium-rich granite. If you start seeing pyrophanite, elpidite, monazite in float, you are in the right ground. Typical habit: anhedral grains, prismatic, striated. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify janhaugite?+
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What rocks look like janhaugite?+
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Find janhaugite on the map
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