Sekaninaite is the iron-dominant member of the cordierite group, typically occurring in granite pegmatites. It is often visually indistinguishable from cordierite without laboratory analysis, generally forming blue-violet prismatic crystals or granular aggregates within pegmatitic rocks.
Is this sekaninaite?
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 sekaninaite with a known reference. Sekaninaite sits at Mohs 7-7.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Sekaninaite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Sekaninaite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: blue, blue-violet, grayish-blue.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: short prismatic crystals, granular, massive.
Often confused with
Sekaninaite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside sekaninaite
Minerals reported to co-occur with sekaninaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Fe²⁺,Mg)₂Al₄Si₅O₁₈
- Mohs hardness
- 7-7.5
- Density
- 2.78-2.82 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Short Prismatic Crystals, Granular, Massive
- Cleavage
- Distinct On {010}, Poor On {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $20-150 per specimen depending on crystal size
Where rockhounds find sekaninaite
Classic worldwide localities
- Dolni Bory, Czech Republic
- Manitoba, Canada
Field-hunting tip
Look in granite pegmatites country — that is the host setting where sekaninaite typically forms. If you start seeing quartz, k-feldspar, biotite in float, you are in the right ground. Field specimens usually show a short prismatic crystals, granular, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find sekaninaite on the map
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