Trigonite is a rare lead-manganese arsenite mineral found almost exclusively in the famous Långban mining district of Sweden. It typically occurs as small, pale yellow to brownish-yellow tabular crystals or aggregates within manganese-rich skarns.
Is this trigonite?
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 trigonite with a known reference. Trigonite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to adamantine.
- 4Match the color rangeCompare against the expected color range: yellow, brown, yellow brown, sulfur yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals.
Often confused with
Trigonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Trigonite leaves yellow, Mimetite leaves white; luster reads vitreous to adamantine on Trigonite and resinous to subadamantine on Mimetite.
How to tell apart: Streak differs, so Trigonite leaves yellow, Hectorite leaves white; luster reads vitreous to adamantine on Trigonite and earthy to waxy, dull on Hectorite.
Often found alongside trigonite
Minerals reported to co-occur with trigonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₃Mn(AsO₃)₂(AsO₂OH)
- Mohs hardness
- 2-3
- Density
- 6.1-7.1 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Vitreous to adamantine
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals
- Cleavage
- {010}, perfect; {101}, good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a metamorphosed Fe–Mn orebody
Where rockhounds find trigonite
Classic worldwide localities
- Långban, Värmland, Sweden
Field-hunting tip
Where it forms: In a metamorphosed Fe–Mn orebody. If you start seeing lead, dixenite, hausmannite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify trigonite?+
Where is trigonite found?+
Is trigonite safe to handle?+
What rocks look like trigonite?+
What minerals are found with trigonite?+
What kind of rock does trigonite form in?+
What is trigonite used for?+
Find trigonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
