Ježekite is a rare sodium uranium sulfate, typically sulfuric-yellow. It was approved as a distinct mineral species in 2014. It was first described from Geschieber vein, Svornost mine, Jáchymov, Western Bohemia, Czech Republic.
Is this ježekite?
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 ježekite with a known reference. Ježekite sits at Mohs ~2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to pearly.
- 4Match the color rangeCompare against the expected color range: sulfuric-yellow.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: tabular crystals.
Often confused with
Ježekite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Cerussite is the harder of the two (Mohs 3-3.5 vs. ~2); streak differs, so Ježekite leaves pale yellow, Cerussite leaves white; luster reads vitreous to pearly on Ježekite and adamantine, tending toward vitreous, resinous on Cerussite.
How to tell apart: Streak differs, so Ježekite leaves pale yellow, Phosgenite leaves white; luster reads vitreous to pearly on Ježekite and adamantine on Phosgenite.
Often found alongside ježekite
Minerals reported to co-occur with ježekite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₈[(UO₂)(CO₃)₃](SO₄)₂·3H₂O
- Mohs hardness
- ~2
- Density
- 2.966 g/cm³
- Colors
- Sulfuric-yellow
- Streak
- Pale yellow
- Luster
- Vitreous to pearly
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Tabular crystals
- Cleavage
- Perfect on {0001}; good on {101̄0}
- Fluorescence
- Fluoresces bright greenish white under LW and SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As crusts, a secondary, low-temperature mineral formed by the alteration of uraninite during post-mining weathering of a hydrothermal vein-type (Ag-Bi-Co-Ni-U) deposit
Where rockhounds find ježekite
Classic worldwide localities
- Geschieber vein, Svornost mine, Jáchymov, Western Bohemia, Czech Republic
Field-hunting tip
Where it forms: As crusts, a secondary, low-temperature mineral formed by the alteration of uraninite during post-mining weathering of a hydrothermal vein-type (Ag-Bi-Co-Ni-U) deposit. If you start seeing andersonite, čejkaite, schröckingerite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find ježekite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
