Turtmannite is a rare manganese vanadate that forms bright yellow flakes. It occurs in metamorphosed (upper greenschist facies) jacobsite-rich Fe-Mn ores in paleokarst. Associated minerals include jacobsite, kutnohorite and baryte. It was first described from Turtmann Valley, Valais, Switzerland.
Is this turtmannite?
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 turtmannite with a known reference. Turtmannite 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. Streak: colorless.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: bright yellow, orange.
- 5Look at form & habitCrystal system: trigonal. Typical habit: anhedral grains, micaceous, prismatic.
Often confused with
Turtmannite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Turtmannite leaves colorless, Tilasite leaves white; luster reads vitreous on Turtmannite and resinous, vitreous on cleavages on Tilasite.
How to tell apart: Streak differs, so Turtmannite leaves colorless, Magnussonite leaves white.
Often found alongside turtmannite
Minerals reported to co-occur with turtmannite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn₂₅O₅(VO₄)₃(SiO₄)₃(OH)₂₀
- Mohs hardness
- 4-5
- Density
- 3.6-4.0 g/cm³
- Colors
- Streak
- Colorless
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Anhedral grains, micaceous, prismatic
- Cleavage
- Perfect on {0001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In metamorphosed (upper greenschist facies) jacobsite-rich Fe-Mn ores in paleokarst
Where rockhounds find turtmannite
Classic worldwide localities
- Turtmann Valley, Valais, Switzerland
Field-hunting tip
Where it forms: In metamorphosed (upper greenschist facies) jacobsite-rich Fe-Mn ores in paleokarst. If you start seeing jacobsite, kutnohorite, baryte in float, you are in the right ground. Typical habit: anhedral grains, micaceous, prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify turtmannite?+
Where is turtmannite found?+
Is turtmannite safe to handle?+
What rocks look like turtmannite?+
What minerals are found with turtmannite?+
What kind of rock does turtmannite form in?+
What is turtmannite used for?+
Find turtmannite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
