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, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: black, brownish black.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: disseminated, granular.
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, so Tapiolite-(Fe) leaves brown, Columbite leaves blackish brown; luster reads metallic on Tapiolite-(Fe) and submetallic on Columbite.
How to tell apart: Streak differs, so Tapiolite-(Fe) leaves brown, Cassiterite leaves white, pale brown, pale gray; luster reads metallic on Tapiolite-(Fe) and adamantine to adamantine metallic, splendent; may be greasy on fractures on Cassiterite.
How to tell apart: Streak differs, so Tapiolite-(Fe) leaves brown, Rutile leaves pale brown, yellowish brown; gray, greenish black with high nb–ta; luster reads metallic on Tapiolite-(Fe) and adamantine to submetallic 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
- Density
- 7.82 g/cm³
- Colors
- Streak
- Brown
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Tetragonal
- Crystal habit
- Disseminated, granular
- Cleavage
- Imperfect on {110}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Pegmatites and alluvial deposits
Where rockhounds find tapiolite-(fe)
Classic worldwide localities
- Sri Lanka (type locality)
Field-hunting tip
Where it forms: Pegmatites and alluvial deposits. If you start seeing albite, quartz, microcline in float, you are in the right ground. Typical habit: disseminated, granular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify tapiolite-(fe)?+
Where is tapiolite-(fe) found?+
What rocks look like tapiolite-(fe)?+
What minerals are found with tapiolite-(fe)?+
What kind of rock does tapiolite-(fe) form in?+
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Find tapiolite-(fe) on the map
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