Lehmannite is a rare sodium copper titanium arsenate. It is a sublimate around an active volcanic fumarole. It was first described from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia.
Is this lehmannite?
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 lehmannite with a known reference. Lehmannite 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: grayish green with olive hue.
- 3Read the lusterHold the specimen under a strong light. Luster: strong vitreous.
- 4Match the color rangeCompare against the expected color range: dark grayish green, olive-greenish black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals.
Often confused with
Lehmannite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Beryl is the harder of the two (Mohs 7.5-8 vs. ~4.5); streak differs, so Lehmannite leaves grayish green with olive hue, Beryl leaves white; luster reads strong vitreous on Lehmannite and vitreous, resinous on Beryl.
How to tell apart: Citrine is the harder of the two (Mohs 7 vs. ~4.5); streak differs, so Lehmannite leaves grayish green with olive hue, Citrine leaves white; luster reads strong vitreous on Lehmannite and vitreous on Citrine.
How to tell apart: Topaz is the harder of the two (Mohs 8 vs. ~4.5); streak differs, so Lehmannite leaves grayish green with olive hue, Topaz leaves white; luster reads strong vitreous on Lehmannite and vitreous on Topaz.
Often found alongside lehmannite
Minerals reported to co-occur with lehmannite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₁₈Cu₁₂TiO₈(AsO₄)₈FCl₅
- Mohs hardness
- ~4.5
- Density
- 3.676 g/cm³
- Colors
- Dark grayish greenOlive-greenish black
- Streak
- Grayish green with olive hue
- Luster
- Strong vitreous
- Transparency
- Translucent to nearly opaque
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Gemstone
- Host rock
- A sublimate around an active volcanic fumarole
Where rockhounds find lehmannite
Classic worldwide localities
- Arsenatnaya fumarole, Second scoria cone, Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia
Field-hunting tip
Where it forms: A sublimate around an active volcanic fumarole. If you start seeing arsmirandite, hematite, sanidine in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find lehmannite on the map
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