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, 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.
