Aspedamite is a rare iron niobium thorium hydroxide, typically brownish orange to deep red. It occurs in a complex granitic pegmatite on altered monazite. It was first described from Herrebøkasa quarry, 2 km north-northeast of Aspedammen, Østfold county, Norway.
Is this aspedamite?
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 aspedamite with a known reference. Aspedamite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Aspedamite leaves a very pale orange streak.
- 3Read the lusterHold the specimen under a strong light. Aspedamite typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: brownish orange, deep red.
- 5Look at form & habitCrystal system: cubic. Typical habit: massive.
Often confused with
Aspedamite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Allanite is the harder of the two (Mohs 5.5-6 vs. 3-4); streak differs, so Aspedamite leaves very pale orange, Allanite leaves gray; luster reads adamantine on Aspedamite and submetallic on Allanite.
How to tell apart: Epidote is the harder of the two (Mohs 6-7 vs. 3-4); streak differs, so Aspedamite leaves very pale orange, Epidote leaves white; luster reads adamantine on Aspedamite and vitreous on Epidote.
Often found alongside aspedamite
Minerals reported to co-occur with aspedamite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- ☐₁₂(Fe³⁺,Fe²⁺)₃Nb₄[Th(Nb,Fe³⁺)₁₂O₄₂][(H₂O),(OH)]₁₂
- Mohs hardness
- 3-4
- Density
- 4.070 g/cm³
- Colors
- Streak
- Very Pale Orange
- Luster
- Adamantine
- Transparency
- Transparent
- Crystal system
- Cubic
- Crystal habit
- Massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Pegmatites
Where rockhounds find aspedamite
Classic worldwide localities
- Aspedam, Østfold, Norway
Field-hunting tip
Look in pegmatites country, the host setting where aspedamite typically forms. If you start seeing microcline, quartz, biotite in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find aspedamite on the map
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