Olmiite is a highly sought-after rare silicate mineral primarily found in the Kalahari Manganese Field. It typically occurs as beautiful, salmon-pink to brown crystalline clusters or drusy coatings on manganese ore specimens. It is easily confused with poldervaartite and often requires chemical testing or XRD for definitive identification.
Is this olmiite?
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 olmiite with a known reference. Olmiite sits at Mohs 5-5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: reddish pink.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic.
Often confused with
Olmiite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside olmiite
Minerals reported to co-occur with olmiite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaMnSiO₃(OH)₂
- Mohs hardness
- 5-5.5
- Density
- 3.05 g/cm³
- Colors
- Reddish pink
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A product of hydrothermal alteration of primary sedimentary and low-grade metamorphic manganese ores
Where rockhounds find olmiite
Classic worldwide localities
- N’Chwaning II mine, Kalahari manganese fields, Republic of South Africa
Field-hunting tip
Where it forms: A product of hydrothermal alteration of primary sedimentary and low-grade metamorphic manganese ores. If you start seeing poldervaartite, celestine, sturmanite in float, you are in the right ground. Typical habit: prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify olmiite?+
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What rocks look like olmiite?+
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Find olmiite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
