Pinakiolite is a rare borate mineral typically found in metamorphosed manganese deposits. It forms dark, prismatic crystals that are often heavily striated, and it is most famous for its occurrences in the classic mining districts of Sweden.
Is this pinakiolite?
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 pinakiolite with a known reference. Pinakiolite 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. Streak: brownish gray.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic, brilliant on {010}, to pearly.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular.
Often confused with
Pinakiolite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Pinakiolite leaves brownish gray, Ludwigite leaves black to greenish black; luster reads metallic, brilliant on {010}, to pearly on Pinakiolite and submetallic on Ludwigite.
How to tell apart: Pinakiolite is noticeably harder (Mohs 6 vs. 5).
Often found alongside pinakiolite
Minerals reported to co-occur with pinakiolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Mg,Mn)₂(Mn,Sb)O₂(BO₃)
- Mohs hardness
- 6
- Density
- 3.88 g/cm³
- Colors
- Streak
- Brownish gray
- Luster
- Metallic, brilliant on {010}, to pearly
- Transparency
- Opaque to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular
- Cleavage
- Good on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare mineral in banded granular dolomite in a metamorphosed Fe–Mn orebody
Where rockhounds find pinakiolite
Classic worldwide localities
- Långban, Värmland, Sweden
Field-hunting tip
Where it forms: A rare mineral in banded granular dolomite in a metamorphosed Fe–Mn orebody. If you start seeing hausmannite, tephroite, berzeliite in float, you are in the right ground. Typical habit: tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify pinakiolite?+
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Find pinakiolite on the map
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