Ekplexite is a rare niobium molybdenum magnesium hydroxide, typically iron black. It was approved as a distinct mineral species in 2011. It was first described from Mt. Kaskasnyunchorr, Khibiny alkaline complex, Kola Peninsula, Russia.
Is this ekplexite?
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 ekplexite with a known reference. Ekplexite sits at Mohs ~1, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: iron black.
- 5Look at form & habitCrystal system: trigonal. Typical habit: platy or micaceous aggregates.
Often confused with
Ekplexite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ekplexite leaves black, Molybdenite leaves bluish gray.
How to tell apart: Bismuthinite is the harder of the two (Mohs 2-2.5 vs. ~1); streak differs, so Ekplexite leaves black, Bismuthinite leaves lead-gray.
Often found alongside ekplexite
Minerals reported to co-occur with ekplexite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Nb,Mo)S₂·(Mg₁₋ₓAlₓ)(OH)₂₊ₓ
- Mohs hardness
- ~1
- Density
- 3.63 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Platy or micaceous aggregates
- Cleavage
- Perfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Of hydrothermal origin in fenites formed by a peralkaline fluid, as a source of Nb, reacting with a large xenolith of alumina-rich metamorphic rocks (metapelites) in agpaitic nepheline syenite
Where rockhounds find ekplexite
Classic worldwide localities
- Mt. Kaskasnyunchorr, Khibiny alkaline complex, Kola Peninsula, Russia
Field-hunting tip
Where it forms: Of hydrothermal origin in fenites formed by a peralkaline fluid, as a source of Nb, reacting with a large xenolith of alumina-rich metamorphic rocks (metapelites) in agpaitic nepheline syenite. If you start seeing orthoclase, anorthoclase, nepheline in float, you are in the right ground. Typical habit: platy or micaceous aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
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Find ekplexite on the map
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