Ferrowodginite is an extremely rare tantalum oxide mineral typically found in complex, highly fractionated granite pegmatites. It usually forms as small, dark, submetallic crystals associated with other rare earth and tantalum-bearing minerals.
Is this ferrowodginite?
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 ferrowodginite with a known reference. Ferrowodginite sits at Mohs 5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: dark brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: black, dark brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: equant to tabular crystals.
Often confused with
Ferrowodginite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ferrowodginite leaves dark brown, Wodginite leaves brown; luster reads vitreous on Ferrowodginite and submetallic on Wodginite.
How to tell apart: Streak differs, so Ferrowodginite leaves dark brown, Columbite leaves blackish brown; luster reads vitreous on Ferrowodginite and submetallic on Columbite.
Often found alongside ferrowodginite
Minerals reported to co-occur with ferrowodginite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeSnTa₂O₈
- Mohs hardness
- 5.5
- Density
- 7.02 g/cm³
- Colors
- Streak
- Dark brown
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Equant to tabular crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- In museum specimens from a granite pegmatite
Where rockhounds find ferrowodginite
Classic worldwide localities
- Sukula, Tammela, Finland, the exact locality now lost
Field-hunting tip
Where it forms: In museum specimens from a granite pegmatite. If you start seeing tantalian cassiterite, tapiolite, bismuth in float, you are in the right ground. Typical habit: equant to tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferrowodginite?+
Where is ferrowodginite found?+
What rocks look like ferrowodginite?+
What minerals are found with ferrowodginite?+
What kind of rock does ferrowodginite form in?+
What is ferrowodginite used for?+
Find ferrowodginite on the map
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