Ferroindialite is a rare hexagonal member of the indialite-cordierite series, distinguished by its high iron content. It is typically found in high-temperature, low-pressure pyrometamorphic environments where it forms small, prism-shaped crystals. It is nearly indistinguishable from ordinary cordierite without advanced X-ray diffraction or chemical analysis.
Is this ferroindialite?
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 ferroindialite with a known reference. Ferroindialite 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. Ferroindialite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Ferroindialite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: blue, colorless, gray.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: hexagonal prisms, massive.
Often confused with
Ferroindialite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside ferroindialite
Minerals reported to co-occur with ferroindialite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Mg,Fe)₂Al₄Si₅O₁₈
- Mohs hardness
- 7-7.5
- Density
- 2.6-2.7 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Hexagonal
- Crystal habit
- Hexagonal Prisms, Massive
- Cleavage
- Poor On {0001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Pyrometamorphic Rocks
- Typical price
- $50-300 per specimen
Where rockhounds find ferroindialite
Classic worldwide localities
- Bocche di Bonifacio, Sardinia
- various pyrometamorphic complexes
Field-hunting tip
Look in pyrometamorphic rocks country, the host setting where ferroindialite typically forms. If you start seeing quartz, feldspar, mullite in float, you are in the right ground. Field specimens usually show a hexagonal prisms, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferroindialite?+
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Find ferroindialite on the map
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