Ramsdellite is a manganese oxide mineral typically found as metallic, black prismatic to needle-like crystals or massive, fibrous aggregates. It is often confused with pyrolusite, though it is usually distinguished by its orthorhombic structure and distinct cleavage. Collectors primarily seek out well-defined bladed crystals from famous historical manganese localities.
Is this ramsdellite?
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 ramsdellite with a known reference. Ramsdellite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ramsdellite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Ramsdellite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: black, gray.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic crystals, massive, fibrous, platy.
Often confused with
Ramsdellite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Pyrolusite is the harder of the two (Mohs 6-6.5 vs. 3).
How to tell apart: Nsutite is the harder of the two (Mohs 6-6.5 vs. 3); streak differs, so Ramsdellite leaves black, Nsutite leaves dark brown; luster reads metallic on Ramsdellite and submetallic on Nsutite.
How to tell apart: Manganite is the harder of the two (Mohs 4 vs. 3); streak differs, so Ramsdellite leaves black, Manganite leaves dark reddish-brown; luster reads metallic on Ramsdellite and submetallic on Manganite.
Often found alongside ramsdellite
Minerals reported to co-occur with ramsdellite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MnO₂
- Mohs hardness
- 3
- Density
- 4.8 g/cm³
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic Crystals, Massive, Fibrous, Platy
- Cleavage
- Perfect in One Direction
- Rarity
- Uncommon
- Uses
- Collector, Ore of Manganese
- Host rock
- Sedimentary Manganese Deposits, Hydrothermal Veins
- Typical price
- $10-60 per specimen depending on crystal definition
Where rockhounds find ramsdellite
Classic worldwide localities
- Lake Valley, New Mexico, USA
- Sitapar, India
- Tanzanite, Tanzania
- Postmasburg, South Africa
Field-hunting tip
Look in sedimentary manganese deposits, hydrothermal veins country, the host setting where ramsdellite typically forms. If you start seeing pyrolusite, lithiophorite, goethite in float, you are in the right ground. Field specimens usually show a prismatic crystals, massive, fibrous, platy habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ramsdellite on the map
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