Foordite is a rare tin-niobium oxide belonging to the tapiolite group. It is primarily found in granitic pegmatite environments and is visually difficult to distinguish from other dark, opaque oxide minerals without chemical analysis. Collectors typically seek it for its rarity and its specific association with pegmatite mineral suites.
Is this foordite?
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 foordite with a known reference. Foordite sits at Mohs 6-6.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Foordite leaves a yellowish white streak.
- 3Read the lusterHold the specimen under a strong light. Foordite typically shows a vitreous to adamantine luster.
- 4Match the color rangeCompare against the expected color range: black, brownish-black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic to tabular crystals.
Often confused with
Foordite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Foordite leaves yellowish white, Columbium Ore leaves dark red to black; luster reads vitreous to adamantine on Foordite and submetallic on Columbium Ore.
How to tell apart: Streak differs, so Foordite leaves yellowish white, Cassiterite leaves white; luster reads vitreous to adamantine on Foordite and adamantine on Cassiterite.
Often found alongside foordite
Minerals reported to co-occur with foordite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Sn,Fe)Nb₂O₆
- Mohs hardness
- 6-6.5
- Density
- 6.734 g/cm³
- Colors
- Streak
- Yellowish White
- Luster
- Vitreous to Adamantine
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic to Tabular Crystals
- Cleavage
- {100}, Perfect; {011}, Poor
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Granite Pegmatites
Where rockhounds find foordite
Classic worldwide localities
- 15 km north-northwest of Lutsiro, near the Sebeya River, western Rwanda
Field-hunting tip
Look in granite pegmatites country, the host setting where foordite typically forms. If you start seeing quartz, albite, muscovite in float, you are in the right ground. Field specimens usually show a prismatic to tabular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify foordite?+
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What rocks look like foordite?+
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Find foordite on the map
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