Trilithionite is a lithium-rich mica belonging to the lepidolite series. It occurs primarily in complex pegmatites and is often visually indistinguishable from other lepidolite-group micas without chemical analysis, typically presenting as small, scaly, micaceous plates.
Is this trilithionite?
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 trilithionite with a known reference. Trilithionite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: micaceous.
Often confused with
Trilithionite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads vitreous on Trilithionite and pearly to vitreous on Lepidolite.
How to tell apart: Luster reads vitreous on Trilithionite and pearly to waxy when fine-grained on Polylithionite.
Often found alongside trilithionite
Minerals reported to co-occur with trilithionite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KLi₁.₅Al₁.₅(Si₃Al)O₁₀F₂
- Mohs hardness
- 2.5-3
- Density
- 2.8-3.0 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Micaceous
- Cleavage
- Perfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Intermediate composition near polylithionite
Where rockhounds find trilithionite
Classic worldwide localities
- Hagendorf, Germany
- Varuträsk, Sweden
- Tanco Mine, Canada
Field-hunting tip
Where it forms: Intermediate composition near polylithionite. If you start seeing quartz, albite, microcline in float, you are in the right ground. Typical habit: micaceous. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify trilithionite?+
Where is trilithionite found?+
What rocks look like trilithionite?+
What minerals are found with trilithionite?+
What kind of rock does trilithionite form in?+
What is trilithionite used for?+
Find trilithionite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
