Zussmanite is a rare phyllosilicate mineral typically found in high-pressure, low-temperature metamorphic environments such as blueschist facies. It usually appears as fine-grained, platy, or radiating aggregates with a distinct green or brown coloration. It is primarily known from its type locality near Laytonville, California, where it forms in association with other silicates.
Is this zussmanite?
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 zussmanite with a known reference. Zussmanite sits at Mohs 3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Zussmanite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Zussmanite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: green, brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: platy crystals.
Often confused with
Zussmanite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Zussmanite leaves white, Stilpnomelane leaves yellowish-brown to greenish-black; luster reads vitreous on Zussmanite and pearly on Stilpnomelane.
How to tell apart: Luster reads vitreous on Zussmanite and pearly on Biotite.
Often found alongside zussmanite
Minerals reported to co-occur with zussmanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K(Fe,Mg,Mn)₁₃(Si,Al)₁₈O₄₂(OH)₁₄
- Mohs hardness
- 3
- Density
- 3.16 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Platy Crystals
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphic Blueschist Facies
- Typical price
- $20-150 per specimen
Where rockhounds find zussmanite
Classic worldwide localities
- Laytonville, California, USA
Field-hunting tip
Look in metamorphic blueschist facies country — that is the host setting where zussmanite typically forms. If you start seeing quartz, stilpnomelane, riebeckite in float, you are in the right ground. Field specimens usually show a platy crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find zussmanite on the map
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