Tainiolite is a rare lithium-bearing mica characterized by its distinct, flexible, and elastic platy cleavage. It is typically found in alkaline igneous rocks or pegmatites, often occurring as small, pearly flakes or thin sheets that require careful observation for identification.
Is this tainiolite?
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 tainiolite with a known reference. Tainiolite sits at Mohs 2.5-3.5, 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, silky.
- 4Match the color rangeCompare against the expected color range: colorless, brownish, greenish brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: foliated, micaceous.
Often confused with
Tainiolite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads vitreous, silky on Tainiolite and pearly to submetallic on cleavage on Phlogopite.
How to tell apart: Luster reads vitreous, silky on Tainiolite and pearly to vitreous on Lepidolite.
Often found alongside tainiolite
Minerals reported to co-occur with tainiolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KLiMg₂Si₄O₁₀F₂
- Mohs hardness
- 2.5-3.5
- Density
- 2.83-2.90 g/cm³
- Streak
- White
- Luster
- Vitreous, silky
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Foliated, micaceous
- Cleavage
- {001}, perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A late-stage mineral in nepheline syenite pegmatites
Where rockhounds find tainiolite
Classic worldwide localities
- Magnet Cove, Hot Spring Co., Arkansas, and Coyote Peak, near Orick, Humboldt Co., California, USA
- Narssârssuk, Greenland
- Lovozero and Khibiny massifs, Kola Peninsula, and at several poorly defined localities around Lake Baikal, Siberia, Russia
- Mont Saint-Hilaire, Quebec, Canada
Field-hunting tip
Where it forms: A late-stage mineral in nepheline syenite pegmatites. If you start seeing quartz, dickite, natrolite in float, you are in the right ground. Typical habit: foliated, micaceous. Train your eye for that shape before scanning the outcrop.
Common questions
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Find tainiolite on the map
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