Ganophyllite is a rare manganese phyllosilicate mineral characterized by its distinct pearly luster and perfect micaceous cleavage. It is typically found as brown, foliated masses or platy crystals within metamorphosed manganese ore bodies, often appearing alongside other manganese-rich minerals like jacobsite.
Is this ganophyllite?
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 ganophyllite with a known reference. Ganophyllite sits at Mohs 4-4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brownish yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous, brilliant.
- 4Match the color rangeCompare against the expected color range: brownish yellow, cinnamon brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: foliated, micaceous.
Often confused with
Ganophyllite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside ganophyllite
Minerals reported to co-occur with ganophyllite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (K,Na)₂Mn₆(Si,Al)₁₀O₂₄(OH)₄·7-11H₂O
- Mohs hardness
- 4-4.5
- Density
- 2.77-2.84 g/cm³
- Colors
- Brownish yellowCinnamon brown
- Streak
- Brownish yellow
- Luster
- Vitreous, brilliant
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Foliated, micaceous
- Cleavage
- Perfect micaceous on {001}; distinct on {100}, {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In manganese-rich portions of metamorphosed Zn-Mn mineral deposits
Where rockhounds find ganophyllite
Classic worldwide localities
- Maple-Hovey deposits, west of Bridgewater, Aroostook Co., Maine, and at Franklin, Sussex Co., New Jersey, USA
- Harstigen mine, near Persberg, and at Långban, Värmland, Sweden
- Sjö mine, near Grythyttan, Örebro, Sweden
- Benallt and Nant mines, Rhiw, Lleyn Peninsula, Wales
- Molinello and Gambatesa manganese mines, near Chiavari, Val Graveglia, Liguria, Italy
- Mont Saint-Hilaire, Quebec, Canada
Field-hunting tip
Where it forms: In manganese-rich portions of metamorphosed Zn-Mn mineral deposits. If you start seeing calcite, rhodonite, caryopilite in float, you are in the right ground. Typical habit: foliated, micaceous. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ganophyllite?+
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Find ganophyllite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
