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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: light green.
- 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, so Zussmanite leaves white, Stilpnomelane leaves gray white; luster reads vitreous on Zussmanite and pearly to vitreous on cleavage surface, may be submetallic on Stilpnomelane.
How to tell apart: Luster reads vitreous on Zussmanite and splendent to submetallic, vitreous, pearly on cleavage 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
- 3.146 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Platy crystals
- Cleavage
- {0001}, perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In an exotic block of metamorphosed shales, siliceous ironstones, and impure limestones, probably representing deep ocean sediments subjected to blueschist facies metamorphism
Where rockhounds find zussmanite
Classic worldwide localities
- Laytonville quarry, Mendocino Co., California, USA
Field-hunting tip
Where it forms: In an exotic block of metamorphosed shales, siliceous ironstones, and impure limestones, probably representing deep ocean sediments subjected to blueschist facies metamorphism. If you start seeing deerite, howieite, stilpnomelane in float, you are in the right ground. Typical habit: platy crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify zussmanite?+
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What rocks look like zussmanite?+
What minerals are found with zussmanite?+
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Find zussmanite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
