Franconite is a rare niobium-bearing mineral typically found as white, platy, or fan-shaped crystalline aggregates. It is almost exclusively known to collectors from the alkaline intrusive complexes in Quebec, particularly the Francon and Poudrette quarries where it occurs in vugs within igneous rocks.
Is this franconite?
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 franconite with a known reference. Franconite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Franconite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Franconite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: white, yellowish-white, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, radial aggregates, coatings.
Often confused with
Franconite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Franconite leaves white, Ikunolite leaves gray; luster reads pearly on Franconite and metallic on Ikunolite.
How to tell apart: Gonnardite is the harder of the two (Mohs 5 vs. 2); luster reads pearly on Franconite and vitreous on Gonnardite.
Often found alongside franconite
Minerals reported to co-occur with franconite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂Nb₄O₁₁·9H₂O
- Mohs hardness
- 2
- Density
- 2.44 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Radial Aggregates, Coatings
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Intrusive Rocks
- Typical price
- $50-300 per specimen
Where rockhounds find franconite
Classic worldwide localities
- Poudrette quarry, Mont Saint-Hilaire, Quebec, Canada
- Francon quarry, Montreal, Quebec, Canada
Field-hunting tip
Look in alkaline igneous intrusive rocks country — that is the host setting where franconite typically forms. If you start seeing quartz, microcline, dawsonite in float, you are in the right ground. Field specimens usually show a platy crystals, radial aggregates, coatings habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find franconite on the map
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