Bementite is a rare manganese silicate typically found as dense, massive, or foliated aggregates. It is best known to collectors from the famous zinc-manganese mines of Franklin and Sterling Hill, New Jersey, where it is often associated with other rare manganese minerals.
Is this bementite?
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 bementite with a known reference. Bementite sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Bementite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Bementite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: brown, yellowish-brown, reddish-brown, yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: massive, foliated, fibrous.
Often confused with
Bementite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside bementite
Minerals reported to co-occur with bementite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn₈Si₆O₁₅(OH)₁₀
- Mohs hardness
- 6
- Density
- 3.0-3.1 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Massive, Foliated, Fibrous
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphosed Manganese Ore Deposits
- Typical price
- $20-150 for small specimens
Where rockhounds find bementite
2 mapped spotsClassic worldwide localities
- Franklin, New Jersey, USA
- Sterling Hill, New Jersey, USA
- Kajiwara, Japan
- Moosburg, Austria
Field-hunting tip
Look in metamorphosed manganese ore deposits country — that is the host setting where bementite typically forms. If you start seeing willemite, franklinite, zincite in float, you are in the right ground. Field specimens usually show a massive, foliated, fibrous habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in California — start trip planning there.
Common questions
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Find bementite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
