Bannisterite is a complex sheet silicate that typically appears as thin, platy crystals in shades of brown or pink. It is most famous as a rare component of the unique mineral assemblages found in the Franklin and Sterling Hill mines of New Jersey. Collectors should look for its distinctive pearly luster on cleavage surfaces when examining specimens from manganese-rich deposits.
Is this bannisterite?
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 bannisterite with a known reference. Bannisterite sits at Mohs 4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Bannisterite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Bannisterite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: brown, pink, white, yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, radial aggregates.
Often confused with
Bannisterite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside bannisterite
Minerals reported to co-occur with bannisterite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (K,Na,Ca)(Mn,Fe,Zn,Mg,Be)₂₁Si₂₅O₆₂(OH,F)₁₆·n(H₂O)
- Mohs hardness
- 4
- Density
- 2.81 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Radial Aggregates
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphosed Zinc-iron-manganese Ore Deposits
- Typical price
- $50-500 depending on specimen quality and size
Where rockhounds find bannisterite
Classic worldwide localities
- Franklin Mine, New Jersey, USA
- Sterling Hill Mine, New Jersey, USA
- Broken Hill, New South Wales, Australia
- Kombat Mine, Namibia
Field-hunting tip
Look in metamorphosed zinc-iron-manganese ore deposits country — that is the host setting where bannisterite typically forms. If you start seeing willemite, franklinite, zincite in float, you are in the right ground. Field specimens usually show a platy crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify bannisterite?+
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How much is bannisterite worth?+
What rocks look like bannisterite?+
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Find bannisterite on the map
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