Zinnwaldite is a lithium-bearing mica that commonly occurs as short, thick tabular crystals or micaceous books. It is most often found in greisens and lithium-rich granite pegmatites, frequently associated with tin and tungsten deposits.
Is this zinnwaldite?
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 zinnwaldite with a known reference. Zinnwaldite sits at Mohs 2.5-4, 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, pearly on cleavage.
- 4Match the color rangeCompare against the expected color range: light brown, silvery white, gray, yellowish white, greenish white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: micaceous, platy, pseudo hexagonal.
Often confused with
Zinnwaldite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads vitreous, pearly on cleavage on Zinnwaldite and splendent to submetallic, vitreous, pearly on cleavage on Biotite.
How to tell apart: Luster reads vitreous, pearly on cleavage on Zinnwaldite and pearly to vitreous on Lepidolite.
Often found alongside zinnwaldite
Minerals reported to co-occur with zinnwaldite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KLiFeAl(AlSi₃)O₁₀(F,OH)₂
- Mohs hardness
- 2.5-4
- Density
- 2.90-3.02 g/cm³
- Streak
- White
- Luster
- Vitreous, pearly on cleavage
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Micaceous, platy, pseudo hexagonal
- Cleavage
- {001}, perfect
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- In tin-bearing pneumatolytic deposits in greisen; more rarely in granites, granite pegmatites, and high-temperature quartz veins
Where rockhounds find zinnwaldite
1 mapped spotsClassic worldwide localities
- Amelia, Amelia Co., Virginia, USA
- Pala district, San Diego Co., and Crestmore, Riverside Co., California, USA
- Black Hills, around Keystone, Pennington Co., South Dakota, USA
- York district, Seward Peninsula, Alaska, USA
- Altenberg, Saxony, and Waldstein, Bavaria, Germany
- Tördal, Norway
Field-hunting tip
Where it forms: In tin-bearing pneumatolytic deposits in greisen; more rarely in granites, granite pegmatites, and high-temperature quartz veins. If you start seeing topaz, cassiterite, wolframite in float, you are in the right ground. Typical habit: micaceous, platy, pseudo hexagonal. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Wisconsin. Start trip planning there.
Common questions
How do you identify zinnwaldite?+
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Find zinnwaldite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
