Katoptrite is a very rare manganese-antimony mineral primarily found in the metamorphosed iron-manganese deposits of Sweden. It typically appears as black, tabular, metallic-lustered crystals associated with other rare manganese minerals in skarn-like environments.
Is this katoptrite?
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 katoptrite with a known reference. Katoptrite sits at Mohs 5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: red brown.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic, brilliant.
- 4Match the color rangeCompare against the expected color range: black, red.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: anhedral grains, tabular.
Often confused with
Katoptrite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Katoptrite leaves red brown, Magnetite leaves black.
How to tell apart: Streak differs, so Katoptrite leaves red brown, Hausmannite leaves dark reddish brown; luster reads metallic, brilliant on Katoptrite and submetallic on Hausmannite.
Often found alongside katoptrite
Minerals reported to co-occur with katoptrite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn₁₃Al₄Sb₂O₂₀(SiO₄)₂
- Mohs hardness
- 5.5
- Density
- 4.56 g/cm³
- Streak
- Red brown
- Luster
- Metallic, brilliant
- Transparency
- Opaque, translucent in thin flakes
- Crystal system
- Monoclinic
- Crystal habit
- Anhedral grains, tabular
- Cleavage
- Perfect micaceous on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In metamorphosed limestone (Brattfors mine, Sweden)
Where rockhounds find katoptrite
Classic worldwide localities
- Brattfors, Moss, and Jakobsberg mines, near Nordmark, and at Långban, Värmland, Sweden
- Sjö mine, near Grythyttan, Örebro, Sweden
Field-hunting tip
Where it forms: In metamorphosed limestone (Brattfors mine, Sweden). If you start seeing magnetite, garnet, manganosite in float, you are in the right ground. Typical habit: anhedral grains, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify katoptrite?+
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Is katoptrite safe to handle?+
What rocks look like katoptrite?+
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Find katoptrite on the map
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