Ianthinite is a rare, highly sensitive uranium-bearing mineral recognizable by its distinct deep violet color. It is an alteration product of uraninite and is often found as a surface coating or in fragile crystal groups, commonly turning into yellow schoepite upon exposure to air.
Is this ianthinite?
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 ianthinite with a known reference. Ianthinite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ianthinite leaves a yellowish-brown streak.
- 3Read the lusterHold the specimen under a strong light. Ianthinite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: deep violet, dark purple.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular, prismatic, or acicular crystals often in radial aggregates.
Often confused with
Ianthinite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Ianthinite leaves yellowish-brown, Becquerelite leaves yellow; luster reads vitreous on Ianthinite and adamantine on Becquerelite.
How to tell apart: Streak differs — Ianthinite leaves yellowish-brown, Masuyite leaves orange-yellow; luster reads vitreous on Ianthinite and adamantine on Masuyite.
How to tell apart: Streak differs — Ianthinite leaves yellowish-brown, Schoepite leaves yellow; luster reads vitreous on Ianthinite and adamantine on Schoepite.
Often found alongside ianthinite
Minerals reported to co-occur with ianthinite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- U⁴⁺(UO₂)₄(OH)₁₄·10H₂O
- Mohs hardness
- 2-3
- Density
- 4.1-4.2 g/cm³
- Colors
- Streak
- Yellowish-brown
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular, Prismatic, Or Acicular Crystals Often in Radial Aggregates
- Cleavage
- Perfect in One Direction
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Uraninite-bearing Hydrothermal Deposits
- Typical price
- $50-500 depending on crystal size and quality
Where rockhounds find ianthinite
Classic worldwide localities
- Shinkolobwe mine (DRC)
- Musonoi mine (DRC)
- Margnac mine (France)
- Wheal Owles (UK)
Field-hunting tip
Look in oxidized zones of uraninite-bearing hydrothermal deposits country — that is the host setting where ianthinite typically forms. If you start seeing uraninite, schoepite, becquerelite in float, you are in the right ground. Field specimens usually show a tabular, prismatic, or acicular crystals often in radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ianthinite on the map
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