Tapiolite-(Fe) is a rare tantalum-bearing oxide that typically occurs as dark, heavy, metallic crystals in granite pegmatites. It is visually very similar to columbite but can often be distinguished by its distinct tetragonal crystal habit and higher density. Collectors value it as a significant ore mineral of tantalum found in complex pegmatite systems.
Is this tapiolite-(fe)?
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 tapiolite-(fe) with a known reference. Tapiolite-(Fe) 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. Tapiolite-(Fe) leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Tapiolite-(Fe) typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: black, brownish-black.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: short prismatic crystals, dipyramidal, granular masses.
Often confused with
Tapiolite-(Fe) vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Tapiolite-(Fe) leaves black, Columbium Ore leaves dark red to black.
How to tell apart: Streak differs — Tapiolite-(Fe) leaves black, Cassiterite leaves white; luster reads submetallic on Tapiolite-(Fe) and adamantine on Cassiterite.
How to tell apart: Streak differs — Tapiolite-(Fe) leaves black, Rutile leaves pale brown to yellow; luster reads submetallic on Tapiolite-(Fe) and metallic to adamantine on Rutile.
Often found alongside tapiolite-(fe)
Minerals reported to co-occur with tapiolite-(fe). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeTa₂O₆
- Mohs hardness
- 6-6.5
- Density
- 7.8-7.9 g/cm³
- Colors
- Streak
- Black
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Tetragonal
- Crystal habit
- Short Prismatic Crystals, Dipyramidal, Granular Masses
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $20-150 for small cabinet specimens
Where rockhounds find tapiolite-(fe)
Classic worldwide localities
- Tammela, Finland
- Greenbushes, Australia
- Minas Gerais, Brazil
- Peerless Pegmatite, South Dakota, USA
Field-hunting tip
Look in granite pegmatites country — that is the host setting where tapiolite-(fe) typically forms. If you start seeing albite, quartz, microcline in float, you are in the right ground. Field specimens usually show a short prismatic crystals, dipyramidal, granular masses habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find tapiolite-(fe) on the map
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