Heftetjernite is a rare scandium tantalum oxide, typically dark brown to greenish brown. It occurs in vugs in albite in a mixed LCT-NYF type cleavelandite-amazonite pegmatite. It was first described from Heftetjern pegmatite, between Høydalen and Skarsfjell, Tørdal, Telemark, Norway.
Is this heftetjernite?
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 heftetjernite with a known reference. Heftetjernite sits at Mohs 4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: dark brown with a reddish hue.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: dark brown, greenish brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: elongate tabular to columnar crystals.
Often confused with
Heftetjernite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Danalite is the harder of the two (Mohs 5.5-6 vs. 4.5); streak differs, so Heftetjernite leaves dark brown with a reddish hue, Danalite leaves gray white; luster reads adamantine on Heftetjernite and vitreous or greasy on Danalite.
How to tell apart: Genthelvite is the harder of the two (Mohs 6.5 vs. 4.5); streak differs, so Heftetjernite leaves dark brown with a reddish hue, Genthelvite leaves white; luster reads adamantine on Heftetjernite and vitreous on Genthelvite.
Often found alongside heftetjernite
Minerals reported to co-occur with heftetjernite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- ScTaO₄
- Mohs hardness
- 4.5
- Density
- 6.44 g/cm³
- Colors
- Streak
- Dark brown with a reddish hue
- Luster
- Adamantine
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Elongate tabular to columnar crystals
- Cleavage
- Perfect on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In vugs in albite in a mixed LCT-NYF type cleavelandite-amazonite pegmatite
Where rockhounds find heftetjernite
Classic worldwide localities
- Heftetjern pegmatite, between Høydalen and Skarsfjell, Tørdal, Telemark, Norway
Field-hunting tip
Where it forms: In vugs in albite in a mixed LCT-NYF type cleavelandite-amazonite pegmatite. If you start seeing albite, fluorite, muscovite in float, you are in the right ground. Typical habit: elongate tabular to columnar crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify heftetjernite?+
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What rocks look like heftetjernite?+
What minerals are found with heftetjernite?+
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Find heftetjernite on the map
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