Kentrolite is a rare lead manganese silicate that typically forms as dark, sub-metallic, radiating prismatic clusters. Collectors most frequently encounter it in specimens from the manganese mines of Sweden or the Franklin mining district in New Jersey. Due to its lead content, it is relatively dense and requires careful handling.
Is this kentrolite?
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 kentrolite with a known reference. Kentrolite sits at Mohs 5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Kentrolite leaves a yellowish-brown streak.
- 3Read the lusterHold the specimen under a strong light. Kentrolite typically shows a resinous luster.
- 4Match the color rangeCompare against the expected color range: dark brown, black, reddish-brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic to acicular crystals, often radiating or in fan-shaped clusters.
Often confused with
Kentrolite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Melanotekite is the harder of the two (Mohs 6.5 vs. 5); streak differs — Kentrolite leaves yellowish-brown, Melanotekite leaves brown; luster reads resinous on Kentrolite and submetallic on Melanotekite.
How to tell apart: Braunite is the harder of the two (Mohs 6-6.5 vs. 5); streak differs — Kentrolite leaves yellowish-brown, Braunite leaves black; luster reads resinous on Kentrolite and submetallic on Braunite.
How to tell apart: Streak differs — Kentrolite leaves yellowish-brown, Allanite leaves gray; luster reads resinous on Kentrolite and submetallic on Allanite.
Often found alongside kentrolite
Minerals reported to co-occur with kentrolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₂Mn₂Si₂O₉
- Mohs hardness
- 5
- Density
- 6.2 g/cm³
- Streak
- Yellowish-brown
- Luster
- Resinous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic to Acicular Crystals, Often Radiating or in Fan-shaped Clusters
- Cleavage
- Distinct in One Direction
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphosed Manganese Ore Deposits
- Typical price
- $50-500 depending on specimen size and crystal quality
Where rockhounds find kentrolite
Classic worldwide localities
- Jakobsberg mine, Sweden
- Franklin, New Jersey, USA
- Langban, Sweden
- Pajsberg, Sweden
Field-hunting tip
Look in metamorphosed manganese ore deposits country — that is the host setting where kentrolite typically forms. If you start seeing hausmannite, barite, andradite in float, you are in the right ground. Field specimens usually show a prismatic to acicular crystals, often radiating or in fan-shaped clusters habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kentrolite?+
Where is kentrolite found?+
How much is kentrolite worth?+
Is kentrolite safe to handle?+
What rocks look like kentrolite?+
What minerals are found with kentrolite?+
What kind of rock does kentrolite form in?+
What is kentrolite used for?+
Find kentrolite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
