Tancaite-(Ce) is a rare iron cerium molybdate that forms red or pale brown octahedral crystals. It is a secondary mineral formed in the oxidation zone of a sulfide ore vein in granite. Associated minerals include quartz, muscovite and molybdenite. It was first described from Su Senargiu, Sarroch, Sardinia, Italy.
Is this tancaite-(ce)?
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 tancaite-(ce) with a known reference. Tancaite-(Ce) sits at Mohs 4-4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to adamantine.
- 4Match the color rangeCompare against the expected color range: red, pale brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: octahedral crystals.
Often confused with
Tancaite-(Ce) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Tancaite-(Ce) leaves yellow, Ferberite leaves brownish black to black; luster reads vitreous to adamantine on Tancaite-(Ce) and submetallic to metallic adamantine on Ferberite.
How to tell apart: Streak differs, so Tancaite-(Ce) leaves yellow, Scheelite leaves white.
Often found alongside tancaite-(ce)
Minerals reported to co-occur with tancaite-(ce). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeCe(MoO₄)₃·3H₂O
- Mohs hardness
- 4-4.5
- Density
- 3.738 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Vitreous to adamantine
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Octahedral crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral formed in the oxidation zone of a sulfide ore vein in granite
Where rockhounds find tancaite-(ce)
Classic worldwide localities
- Su Senargiu, Sarroch (CA), Sardinia, Italy
Field-hunting tip
Where it forms: A secondary mineral formed in the oxidation zone of a sulfide ore vein in granite. If you start seeing quartz, muscovite, molybdenite in float, you are in the right ground. Typical habit: octahedral crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify tancaite-(ce)?+
Where is tancaite-(ce) found?+
What rocks look like tancaite-(ce)?+
What minerals are found with tancaite-(ce)?+
What kind of rock does tancaite-(ce) form in?+
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Find tancaite-(ce) on the map
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